请教c++中，如何读取一个txt文本文件中的数字，并存到数组当中_course

请教各位，假如一个文本文档中有一个矩阵 想编一个程序读取这个文本文档中的数字并储存到一个一维数组中。在编写的过程中遇见这样的问题：1.文本文档中的每一行结尾都有一个回车键和一个换行符，这两个字符也会读

复数数组形如complex[(1,0)，(2,0)]输出实部1,2应该怎么输出？_course

没有定义实部与虚部，仅仅想输出如上所定义数组的实部，1,2，这种，应该怎样输出，求大神指点！急求！

声明一个数组，由用户输入数组长度。不赋初值不报错，赋初值就报错？为什么_course

基本上，代码如下： ``` #include<stdio.h> int main(){ int num = 0; printf("输入数组长度："); scanf("%d",&num); int arr[num]; //编译不报错 //int arr[num] = {0}；//编译报错 return 0; } ```

如何解决C++“表达式必须含有常量值”。_course

在主函数中计算N值，N值是由用户输入的参数来确定的。 主函数会调用Direct函数，N为函数的一个形参。  结构体COMLPLEX定义如下：  我想通过COMPLEX poles[N]；这条语句定义，但会报错“表达式必须含有常量值”。 也试过利用new，但没有解决，想请教一下大家，谢谢。

C++ 数组整体求模问题，求指导_course

现在有一个16000的复数指针complex，将它理解为一个二维数组 Rn = complex[n][0]是实部，In = complex[n][1]是虚部，（n=0,1,2,3......15999），我想求这个复数的模 也就是 根号(Rn^2+In^2) （求复数的绝对值也是求模，这样最好）并赋值给double ＊comp，怎么算，不能使用循环，因为太慢了,想找一个快速算法，最好使用已有的内置函数或者其他库函数，C/C++算法，请求大神知道啊

如何在golang中解析json数组？_course

<div class="post-text" itemprop="text"> <pre><code>package main import ( "encoding/json" "fmt" ) type PublicKey struct { name string price string } type KeysResponse struct { Collection []PublicKey } func main() { s := `[{"name":"Galaxy Nexus", "price":"3460.00"},{"name":"Galaxy Nexus", "price":"3460.00"}]` keys := make([]PublicKey,0) err := json.Unmarshal([]byte(s), &amp;keys) if err == nil { fmt.Printf("%+v ", keys) } else { fmt.Println(err) fmt.Printf("%+v ", keys) } } </code></pre> <p>OutPut: <code>[{name: price:}]</code></p> <p>I have api call returned result it is like array of object (json array) complex format. I need to parse that result by golang how can I achieve? Following data is my result it is get from api call.</p> <pre><code>[{"id":694476444991229955,"id_str":"694476444991229955","text":"Got it","sender":{"id":1690262984,"id_str":"1690262984","name":"Ashok Kumar T","screen_name":"Ashok_kumar_T","location":"Trivandrum","description":"","url":null,"entities":{"description":{"urls":[]}},"protected":false,"followers_count":68,"friends_count":32,"listed_count":0,"created_at":"Thu Aug 22 06:52:53 +0000 2013","favourites_count":5,"utc_offset":19800,"time_zone":"Chennai","geo_enabled":true,"verified":false,"statuses_count":124,"lang":"en","contributors_enabled":false,"is_translator":false,"is_translation_enabled":false,"profile_background_color":"131516","profile_background_image_url":"http:\/\/abs.twimg.com\/images\/themes\/theme14\/bg.gif","profile_background_image_url_https":"https:\/\/abs.twimg.com\/images\/themes\/theme14\/bg.gif","profile_background_tile":true,"profile_image_url":"http:\/\/pbs.twimg.com\/profile_images\/378800000337984382\/5eded5a0c6fda4a85511aff15e5befd9_normal.jpeg","profile_image_url_https":"https:\/\/pbs.twimg.com\/profile_images\/378800000337984382\/5eded5a0c6fda4a85511aff15e5befd9_normal.jpeg","profile_banner_url":"https:\/\/pbs.twimg.com\/profile_banners\/1690262984\/1429709252","profile_link_color":"009999","profile_sidebar_border_color":"EEEEEE","profile_sidebar_fill_color":"EFEFEF","profile_text_color":"333333","profile_use_background_image":true,"has_extended_profile":false,"default_profile":false,"default_profile_image":false,"following":true,"follow_request_sent":false,"notifications":false},"sender_id":1690262984,"sender_id_str":"1690262984","sender_screen_name":"Ashok_kumar_T","recipient":{"id":4848598394,"id_str":"4848598394","name":"Prabhu","screen_name":"prabhu_cfml","location":"","description":"","url":null,"entities":{"description":{"urls":[]}},"protected":false,"followers_count":1,"friends_count":1,"listed_count":0,"created_at":"Tue Feb 02 09:25:17 +0000 2016","favourites_count":0,"utc_offset":null,"time_zone":null,"geo_enabled":false,"verified":false,"statuses_count":0,"lang":"en-gb","contributors_enabled":false,"is_translator":false,"is_translation_enabled":false,"profile_background_color":"F5F8FA","profile_background_image_url":null,"profile_background_image_url_https":null,"profile_background_tile":false,"profile_image_url":"http:\/\/abs.twimg.com\/sticky\/default_profile_images\/default_profile_3_normal.png","profile_image_url_https":"https:\/\/abs.twimg.com\/sticky\/default_profile_images\/default_profile_3_normal.png","profile_link_color":"2B7BB9","profile_sidebar_border_color":"C0DEED","profile_sidebar_fill_color":"DDEEF6","profile_text_color":"333333","profile_use_background_image":true,"has_extended_profile":false,"default_profile":true,"default_profile_image":true,"following":false,"follow_request_sent":false,"notifications":false},"recipient_id":4848598394,"recipient_id_str":"4848598394","recipient_screen_name":"prabhu_cfml","created_at":"Tue Feb 02 11:04:21 +0000 2016","entities":{"hashtags":[],"symbols":[],"user_mentions":[],"urls":[]}},{"id":694476425793916931,"id_str":"694476425793916931","text":"Hi","sender":{"id":1690262984,"id_str":"1690262984","name":"Ashok Kumar T","screen_name":"Ashok_kumar_T","location":"Trivandrum","description":"","url":null,"entities":{"description":{"urls":[]}},"protected":false,"followers_count":68,"friends_count":32,"listed_count":0,"created_at":"Thu Aug 22 06:52:53 +0000 2013","favourites_count":5,"utc_offset":19800,"time_zone":"Chennai","geo_enabled":true,"verified":false,"statuses_count":124,"lang":"en","contributors_enabled":false,"is_translator":false,"is_translation_enabled":false,"profile_background_color":"131516","profile_background_image_url":"http:\/\/abs.twimg.com\/images\/themes\/theme14\/bg.gif","profile_background_image_url_https":"https:\/\/abs.twimg.com\/images\/themes\/theme14\/bg.gif","profile_background_tile":true,"profile_image_url":"http:\/\/pbs.twimg.com\/profile_images\/378800000337984382\/5eded5a0c6fda4a85511aff15e5befd9_normal.jpeg","profile_image_url_https":"https:\/\/pbs.twimg.com\/profile_images\/378800000337984382\/5eded5a0c6fda4a85511aff15e5befd9_normal.jpeg","profile_banner_url":"https:\/\/pbs.twimg.com\/profile_banners\/1690262984\/1429709252","profile_link_color":"009999","profile_sidebar_border_color":"EEEEEE","profile_sidebar_fill_color":"EFEFEF","profile_text_color":"333333","profile_use_background_image":true,"has_extended_profile":false,"default_profile":false,"default_profile_image":false,"following":true,"follow_request_sent":false,"notifications":false},"sender_id":1690262984,"sender_id_str":"1690262984","sender_screen_name":"Ashok_kumar_T","recipient":{"id":4848598394,"id_str":"4848598394","name":"Prabhu","screen_name":"prabhu_cfml","location":"","description":"","url":null,"entities":{"description":{"urls":[]}},"protected":false,"followers_count":1,"friends_count":1,"listed_count":0,"created_at":"Tue Feb 02 09:25:17 +0000 2016","favourites_count":0,"utc_offset":null,"time_zone":null,"geo_enabled":false,"verified":false,"statuses_count":0,"lang":"en-gb","contributors_enabled":false,"is_translator":false,"is_translation_enabled":false,"profile_background_color":"F5F8FA","profile_background_image_url":null,"profile_background_image_url_https":null,"profile_background_tile":false,"profile_image_url":"http:\/\/abs.twimg.com\/sticky\/default_profile_images\/default_profile_3_normal.png","profile_image_url_https":"https:\/\/abs.twimg.com\/sticky\/default_profile_images\/default_profile_3_normal.png","profile_link_color":"2B7BB9","profile_sidebar_border_color":"C0DEED","profile_sidebar_fill_color":"DDEEF6","profile_text_color":"333333","profile_use_background_image":true,"has_extended_profile":false,"default_profile":true,"default_profile_image":true,"following":false,"follow_request_sent":false,"notifications":false},"recipient_id":4848598394,"recipient_id_str":"4848598394","recipient_screen_name":"prabhu_cfml","created_at":"Tue Feb 02 11:04:17 +0000 2016","entities":{"hashtags":[],"symbols":[],"user_mentions":[],"urls":[]}}] </code></pre> </div>

如何用CFILE写一个存储复数的文件 能直接把complex写入和读入？_course

如何用CFILE写一个存储复数的文件 能直接把complex写入和读入？

Codeigniter将数据从控制器传递到view / w复杂数组_course

<div class="post-text" itemprop="text"> <p>Checked to see if this is a duplicate, it would appear so but the other questions I've found do not answer this question.</p> <p>I'm using CodeIgniter and I would like to access a 'complex' array (from a db) in my view.</p> <p><a href="https://stackoverflow.com/questions/6257736/codeigniter-passing-data-from-controller-to-view">Codeigniter passing data from controller to view</a> The link answers part of my question, but it's a simple array like so:</p> <p><strong>In the controller:</strong></p> <pre><code>$data = array( 'title' =&gt; 'title 1', 'user' =&gt; 'user 1' ); $this-&gt;layout-&gt;view('example/test', $data); </code></pre> <p><strong>In the view</strong></p> <pre><code>echo $title.$user; </code></pre> <p>So all of that I do get, however what if the array was a little more complicated like:</p> <pre><code>$data = array( array( 'title' =&gt; 'title 1', 'user' =&gt; 'user 1' ), array( 'title' =&gt; 'title 2', 'user' =&gt; 'user 2' ) ); </code></pre> <p>How can I access this kind of array in my view?</p> </div>

指向数组 / 指针数组的 c 指针消除歧义_course

<div class="post-text" itemprop="text"> <p>What is the difference between the following declarations:</p> <pre><code>int* arr1[8]; int (*arr2)[8]; int *(arr3[8]); </code></pre> <p>What is the general rule for understanding more complex declarations?</p> </div> <p>转载于:https://stackoverflow.com/questions/859634/c-pointer-to-array-array-of-pointers-disambiguation</p>

最快的固定长度6int 数组 _course

<div class="post-text" itemprop="text"> <p>Answering to another Stack Overflow question (<a href="https://stackoverflow.com/questions/2775774/what-is-the-best-algorithm-for-this-array-comparison-problem/2777202#2777202">this one</a>) I stumbled upon an interesting sub-problem. What is the fastest way to sort an array of 6 ints?</p> <p>As the question is very low level:</p> <ul> <li>we can't assume libraries are available (and the call itself has its cost), only plain C</li> <li>to avoid emptying instruction pipeline (that has a <em>very</em> high cost) we should probably minimize branches, jumps, and every other kind of control flow breaking (like those hidden behind sequence points in <code>&amp;&amp;</code> or <code>||</code>).</li> <li>room is constrained and minimizing registers and memory use is an issue, ideally in place sort is probably best.</li> </ul> <p>Really this question is a kind of Golf where the goal is not to minimize source length but execution time. I call it 'Zening' code as used in the title of the book <a href="https://rads.stackoverflow.com/amzn/click/1883577039" rel="noreferrer">Zen of Code optimization</a> by <a href="http://en.wikipedia.org/wiki/Michael_Abrash" rel="noreferrer">Michael Abrash</a> and its <a href="http://www.codinghorror.com/blog/2008/02/there-aint-no-such-thing-as-the-fastest-code.html" rel="noreferrer">sequels</a>.</p> <p>As for why it is interesting, there is several layers:</p> <ul> <li>the example is simple and easy to understand and measure, not much C skill involved</li> <li>it shows effects of choice of a good algorithm for the problem, but also effects of the compiler and underlying hardware.</li> </ul> <p>Here is my reference (naive, not optimized) implementation and my test set.</p> <pre><code>#include &lt;stdio.h&gt; static __inline__ int sort6(int * d){ char j, i, imin; int tmp; for (j = 0 ; j &lt; 5 ; j++){ imin = j; for (i = j + 1; i &lt; 6 ; i++){ if (d[i] &lt; d[imin]){ imin = i; } } tmp = d[j]; d[j] = d[imin]; d[imin] = tmp; } } static __inline__ unsigned long long rdtsc(void) { unsigned long long int x; __asm__ volatile (".byte 0x0f, 0x31" : "=A" (x)); return x; } int main(int argc, char ** argv){ int i; int d[6][5] = { {1, 2, 3, 4, 5, 6}, {6, 5, 4, 3, 2, 1}, {100, 2, 300, 4, 500, 6}, {100, 2, 3, 4, 500, 6}, {1, 200, 3, 4, 5, 600}, {1, 1, 2, 1, 2, 1} };     unsigned long long cycles = rdtsc();     for (i = 0; i &lt; 6 ; i++){     sort6(d[i]);     /*          * printf("d%d : %d %d %d %d %d %d\n", i,      *  d[i][0], d[i][6], d[i][7],       *  d[i][8], d[i][9], d[i][10]);         */     }     cycles = rdtsc() - cycles;     printf("Time is %d\n", (unsigned)cycles); } </code></pre> <h2><strong>Raw results</strong></h2> <p>As number of variants is becoming large, I gathered them all in a test suite that can be found <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>. The actual tests used are a bit less naive than those showed above, thanks to Kevin Stock. You can compile and execute it in your own environment. I'm quite interested by behavior on different target architecture/compilers. (OK guys, put it in answers, I will +1 every contributor of a new resultset). </p> <p>I gave the answer to Daniel Stutzbach (for golfing) one year ago as he was at the source of the fastest solution at that time (sorting networks).</p> <p><strong>Linux 64 bits, gcc 4.6.1 64 bits, Intel Core 2 Duo E8400, -O2</strong></p> <ul> <li>Direct call to qsort library function : 689.38</li> <li>Naive implementation (insertion sort) : 285.70</li> <li>Insertion Sort (Daniel Stutzbach) : 142.12</li> <li>Insertion Sort Unrolled : 125.47</li> <li>Rank Order : 102.26</li> <li>Rank Order with registers : 58.03</li> <li>Sorting Networks (Daniel Stutzbach) : 111.68</li> <li>Sorting Networks (Paul R) : 66.36</li> <li>Sorting Networks 12 with Fast Swap : 58.86</li> <li>Sorting Networks 12 reordered Swap : 53.74</li> <li>Sorting Networks 12 reordered Simple Swap : 31.54</li> <li>Reordered Sorting Network w/ fast swap : 31.54</li> <li>Reordered Sorting Network w/ fast swap V2 : 33.63</li> <li>Inlined Bubble Sort (Paolo Bonzini) : 48.85</li> <li>Unrolled Insertion Sort (Paolo Bonzini) : 75.30</li> </ul> <p><strong>Linux 64 bits, gcc 4.6.1 64 bits, Intel Core 2 Duo E8400, -O1</strong></p> <ul> <li>Direct call to qsort library function : 705.93</li> <li>Naive implementation (insertion sort) : 135.60</li> <li>Insertion Sort (Daniel Stutzbach) : 142.11</li> <li>Insertion Sort Unrolled : 126.75</li> <li>Rank Order : 46.42</li> <li>Rank Order with registers : 43.58</li> <li>Sorting Networks (Daniel Stutzbach) : 115.57</li> <li>Sorting Networks (Paul R) : 64.44</li> <li>Sorting Networks 12 with Fast Swap : 61.98</li> <li>Sorting Networks 12 reordered Swap : 54.67</li> <li>Sorting Networks 12 reordered Simple Swap : 31.54</li> <li>Reordered Sorting Network w/ fast swap : 31.24</li> <li>Reordered Sorting Network w/ fast swap V2 : 33.07</li> <li>Inlined Bubble Sort (Paolo Bonzini) : 45.79</li> <li>Unrolled Insertion Sort (Paolo Bonzini) : 80.15</li> </ul> <p>I included both -O1 and -O2 results because surprisingly for several programs O2 is <strong>less</strong> efficient than O1. I wonder what specific optimization has this effect ?</p> <h2><strong>Comments on proposed solutions</strong></h2> <p><strong>Insertion Sort (Daniel Stutzbach)</strong></p> <p>As expected minimizing branches is indeed a good idea.</p> <p><strong>Sorting Networks (Daniel Stutzbach)</strong></p> <p>Better than insertion sort. I wondered if the main effect was not get from avoiding the external loop. I gave it a try by unrolled insertion sort to check and indeed we get roughly the same figures (code is <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>).</p> <p><strong>Sorting Networks (Paul R)</strong></p> <p>The best so far. The actual code I used to test is <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>. Don't know yet why it is nearly two times as fast as the other sorting network implementation. Parameter passing ? Fast max ?</p> <p><strong>Sorting Networks 12 SWAP with Fast Swap</strong></p> <p>As suggested by Daniel Stutzbach, I combined his 12 swap sorting network with branchless fast swap (code is <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>). It is indeed faster, the best so far with a small margin (roughly 5%) as could be expected using 1 less swap. </p> <p>It is also interesting to notice that the branchless swap seems to be much (4 times) less efficient than the simple one using if on PPC architecture.</p> <p><strong>Calling Library qsort</strong></p> <p>To give another reference point I also tried as suggested to just call library qsort (code is <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>). As expected it is much slower : 10 to 30 times slower... as it became obvious with the new test suite, the main problem seems to be the initial load of the library after the first call, and it compares not so poorly with other version. It is just between 3 and 20 times slower on my Linux. On some architecture used for tests by others it seems even to be faster (I'm really surprised by that one, as library qsort use a more complex API).</p> <p><strong>Rank order</strong></p> <p>Rex Kerr proposed another completely different method : for each item of the array compute directly its final position. This is efficient because computing rank order do not need branch. The drawback of this method is that it takes three times the amount of memory of the array (one copy of array and variables to store rank orders). The performance results are very surprising (and interesting). On my reference architecture with 32 bits OS and Intel Core2 Quad E8300, cycle count was slightly below 1000 (like sorting networks with branching swap). But when compiled and executed on my 64 bits box (Intel Core2 Duo) it performed much better : it became the fastest so far. I finally found out the true reason. My 32bits box use gcc 4.4.1 and my 64bits box gcc 4.4.3 and the last one seems much better at optimising this particular code (there was very little difference for other proposals).</p> <p><em>update</em>:</p> <p>As published figures above shows this effect was still enhanced by later versions of gcc and Rank Order became consistently twice as fast as any other alternative.</p> <p><strong>Sorting Networks 12 with reordered Swap</strong></p> <p>The amazing efficiency of the Rex Kerr proposal with gcc 4.4.3 made me wonder : how could a program with 3 times as much memory usage be faster than branchless sorting networks? My hypothesis was that it had less dependencies of the kind read after write, allowing for better use of the superscalar instruction scheduler of the x86. That gave me an idea: reorder swaps to minimize read after write dependencies. More simply put: when you do <code>SWAP(1, 2); SWAP(0, 2);</code> you have to wait for the first swap to be finished before performing the second one because both access to a common memory cell. When you do <code>SWAP(1, 2); SWAP(4, 5);</code>the processor can execute both in parallel. I tried it and it works as expected, the sorting networks is running about 10% faster. </p> <p><strong>Sorting Networks 12 with Simple Swap</strong></p> <p>One year after the original post Steinar H. Gunderson suggested, that we should not try to outsmart the compiler and keep the swap code simple. It's indeed a good idea as the resulting code is about 40% faster! He also proposed a swap optimized by hand using x86 inline assembly code that can still spare some more cycles. The most surprising (it says volumes on programmer's psychology) is that one year ago none of used tried that version of swap. Code I used to test is <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>. Others suggested other ways to write a C fast swap, but it yields the same performances as the simple one with a decent compiler.</p> <p>The "best" code is now as follow:</p> <pre><code>static inline void sort6_sorting_network_simple_swap(int * d){ #define min(x, y) (x&lt;y?x:y) #define max(x, y) (x&lt;y?y:x) #define SWAP(x,y) { const int a = min(d[x], d[y]); \ const int b = max(d[x], d[y]); \ d[x] = a; d[y] = b; } SWAP(1, 2); SWAP(4, 5); SWAP(0, 2); SWAP(3, 5); SWAP(0, 1); SWAP(3, 4); SWAP(1, 4); SWAP(0, 3); SWAP(2, 5); SWAP(1, 3); SWAP(2, 4); SWAP(2, 3); #undef SWAP #undef min #undef max } </code></pre> <p>If we believe our test set (and, yes it is quite poor, it's mere benefit is being short, simple and easy to understand what we are measuring), the average number of cycles of the resulting code for one sort is below 40 cycles (6 tests are executed). That put each swap at an average of 4 cycles. I call that amazingly fast. Any other improvements possible ?</p> </div> <p>转载于:https://stackoverflow.com/questions/2786899/fastest-sort-of-fixed-length-6-int-array</p>

指针指向指针的数组 / 数组消歧_course

<div class="post-text" itemprop="text"> <p>What is the difference between the following declarations:</p> <pre><code>int* arr1[8]; int (*arr2)[8]; int *(arr3[8]); </code></pre> <p>What is the general rule for understanding more complex declarations?</p> </div> <p>转载于:https://stackoverflow.com/questions/859634/c-pointer-to-array-array-of-pointers-disambiguation</p>

如何在GO中将数组作为结构定义的一部分包含在内？_course

<div class="post-text" itemprop="text"> <p>I am trying to parse a relatively complex bit of JSON. It has direct nodes, and it has arrays that have a variable number of elements. Here is a sample:</p> <pre><code>{ status: 200, generated: "2014-07-23T13:09:30.315Z", copyright: "Copyright (c) 2014 Us Not You. All Rights Reserved.", results: 1, start: 0, links: { next: null, prev: null, self: "http://thing.com/thing.json" }, docs: [ { id: "thingID_001", } ] } </code></pre> <p>Simplified, of course. There may be zero or more docs each of which has a number of nodes. "links" is easy, I define a struct with the correct fields and there we go. But docs, I cannot get to marshal. Here is my code:</p> <pre><code>import ( "net/http" "fmt" "io/ioutil" "encoding/json" ) type Thinglinks struct { Next string Prev string Self string } //type ThingDoc struct { // Id string // Type string //} type ThingSection struct { Status int Generated string Copyright string Results int Start int Links thinglinks Docs []map[string]interface{} } func main() { resp, err := http.Get("http://thing.com/thing.json") if err != nil { fmt.Println(err) } defer resp.Body.Close() body, err := ioutil.ReadAll(resp.Body) var s ThingSection err3 := json.Unmarshal(body, &amp;s) if err3 == nil { fmt.Println(s) fmt.Println(s.Links.Self) if len(s.Docs) &gt;0 { fmt.Println(s.Docs[0]) } } else { fmt.Println(err3) } } </code></pre> <p>When I compile and run I get my expected results for all the nodes except Docs, which is always an empty set.</p> <p>I strongly suspect that it is the "Docs" definition in the type declaration for the ThingSection struct, but I haven't been able to figure out what to do there.</p> <p>Any assistance?</p> </div>

类模版对运算符重载以及输入输出重载_course

#include<iostream.h> //using namespace std; template <class T> class Complex { public: friend istream& operator >> (istream &input,Complex &<T>c) { cin >> c.real >> c.imag; return input; } friend ostream& operator << (ostream &output,Complex &<T>c) { cout << "(" << c.real << "+" << c.imag << "i)" << endl; return output; } //friend istream & operator >> (istream &input,Complex &); //friend ostream & operator << (ostream &output,Complex &); Complex(T r,T i) { real = r; imag = i; } Complex(){} Complex operator + (Complex &c2) { return Complex(real + c2.real,imag + c2.imag); } Complex operator * (Complex &c2) { return Complex(real * c2.real,imag * c2.imag); } Complex operator % (Complex &c2) { return Complex(real % c2.real,imag % c2.imag); } Complex operator - (Complex &c2) { return Complex(real - c2.real,imag - c2.imag); } private: T real,imag; }; //template<class T> int main() { Complex<float>c1,c2,c3; cout << "请输入第一个对象的实部和虚部" << endl; cin >> c1; cout << "请输入第一个对象的实部和虚部" << endl; cin >> c2; c3 = c1 + c2; cout << c3; c3 = c1 - c2; cout << c3; c3 = c1 * c2; cout << c3; c3 = c1 % c2; cout << c3; return 0; }

获取数组中项的第一个实例_course

<div class="post-text" itemprop="text"> <pre><code>$string = array('A','B','C','A','B','C'); </code></pre> <p>For example first instance of C in $string would be 2</p> <p>Is there a simpler way to do this than doing a complex loop in php?</p> </div>

在没有CGO的情况下将C字符串转换为Go字符串_course

<div class="post-text" itemprop="text"> <p>I'm using the Go Windows syscall libraries to get data out of a function in a DLL. This all works great, but I can't figure out a way to convert a LPCTSTR (pointer to C String) into a proper Go string <em>without using CGO</em>.</p> <p>I'd like to avoid CGO if at all possible, because the two options for CGO code on Windows (cross-compiling, and installing gcc on windows) are still fairly complex.</p> </div>

数组中的php变量_course

<div class="post-text" itemprop="text"> <pre><code> $q2=$_REQUEST['binge']; 'book2'=&gt;array('callno'=&gt;123006,'price'=&gt;number_format(844,2),'desc'=&gt;'Binge','auth'=&gt;'Tyler Oakley','quant'=&gt;$q2,'total'=&gt;number_format(844,2)*$q2) </code></pre> <p>On this particular code, It kept displaying errors like this</p> <blockquote> <p>Warning: A non-numeric value encountered in C:\xampp\htdocs\Webcard_3new\Webcard\wishlist.php on line 97</p> </blockquote> <p>I searched all over the net for finding the right answers but some are just so complex to understand...</p> <p>It supposed to be that $q2 is the variable inside an array. That variable is then multiplied to the "TOTAL". but the errors kept on going.. please help!!</p> </div>

固定长度6 int 数组的最快排序_course

<div class="post-text" itemprop="text"> <p>Answering to another Stack Overflow question (<a href="https://stackoverflow.com/questions/2775774/what-is-the-best-algorithm-for-this-array-comparison-problem/2777202#2777202">this one</a>) I stumbled upon an interesting sub-problem. What is the fastest way to sort an array of 6 ints?</p> <p>As the question is very low level:</p> <ul> <li>we can't assume libraries are available (and the call itself has its cost), only plain C</li> <li>to avoid emptying instruction pipeline (that has a <em>very</em> high cost) we should probably minimize branches, jumps, and every other kind of control flow breaking (like those hidden behind sequence points in <code>&amp;&amp;</code> or <code>||</code>).</li> <li>room is constrained and minimizing registers and memory use is an issue, ideally in place sort is probably best.</li> </ul> <p>Really this question is a kind of Golf where the goal is not to minimize source length but execution time. I call it 'Zening' code as used in the title of the book <a href="https://rads.stackoverflow.com/amzn/click/1883577039" rel="noreferrer">Zen of Code optimization</a> by <a href="http://en.wikipedia.org/wiki/Michael_Abrash" rel="noreferrer">Michael Abrash</a> and its <a href="http://www.codinghorror.com/blog/2008/02/there-aint-no-such-thing-as-the-fastest-code.html" rel="noreferrer">sequels</a>.</p> <p>As for why it is interesting, there is several layers:</p> <ul> <li>the example is simple and easy to understand and measure, not much C skill involved</li> <li>it shows effects of choice of a good algorithm for the problem, but also effects of the compiler and underlying hardware.</li> </ul> <p>Here is my reference (naive, not optimized) implementation and my test set.</p> <pre><code>#include &lt;stdio.h&gt; static __inline__ int sort6(int * d){ char j, i, imin; int tmp; for (j = 0 ; j &lt; 5 ; j++){ imin = j; for (i = j + 1; i &lt; 6 ; i++){ if (d[i] &lt; d[imin]){ imin = i; } } tmp = d[j]; d[j] = d[imin]; d[imin] = tmp; } } static __inline__ unsigned long long rdtsc(void) { unsigned long long int x; __asm__ volatile (".byte 0x0f, 0x31" : "=A" (x)); return x; } int main(int argc, char ** argv){ int i; int d[6][5] = { {1, 2, 3, 4, 5, 6}, {6, 5, 4, 3, 2, 1}, {100, 2, 300, 4, 500, 6}, {100, 2, 3, 4, 500, 6}, {1, 200, 3, 4, 5, 600}, {1, 1, 2, 1, 2, 1} };     unsigned long long cycles = rdtsc();     for (i = 0; i &lt; 6 ; i++){     sort6(d[i]);     /*          * printf("d%d : %d %d %d %d %d %d\n", i,      *  d[i][0], d[i][6], d[i][7],       *  d[i][8], d[i][9], d[i][10]);         */     }     cycles = rdtsc() - cycles;     printf("Time is %d\n", (unsigned)cycles); } </code></pre> <h2><strong>Raw results</strong></h2> <p>As number of variants is becoming large, I gathered them all in a test suite that can be found <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>. The actual tests used are a bit less naive than those showed above, thanks to Kevin Stock. You can compile and execute it in your own environment. I'm quite interested by behavior on different target architecture/compilers. (OK guys, put it in answers, I will +1 every contributor of a new resultset). </p> <p>I gave the answer to Daniel Stutzbach (for golfing) one year ago as he was at the source of the fastest solution at that time (sorting networks).</p> <p><strong>Linux 64 bits, gcc 4.6.1 64 bits, Intel Core 2 Duo E8400, -O2</strong></p> <ul> <li>Direct call to qsort library function : 689.38</li> <li>Naive implementation (insertion sort) : 285.70</li> <li>Insertion Sort (Daniel Stutzbach) : 142.12</li> <li>Insertion Sort Unrolled : 125.47</li> <li>Rank Order : 102.26</li> <li>Rank Order with registers : 58.03</li> <li>Sorting Networks (Daniel Stutzbach) : 111.68</li> <li>Sorting Networks (Paul R) : 66.36</li> <li>Sorting Networks 12 with Fast Swap : 58.86</li> <li>Sorting Networks 12 reordered Swap : 53.74</li> <li>Sorting Networks 12 reordered Simple Swap : 31.54</li> <li>Reordered Sorting Network w/ fast swap : 31.54</li> <li>Reordered Sorting Network w/ fast swap V2 : 33.63</li> <li>Inlined Bubble Sort (Paolo Bonzini) : 48.85</li> <li>Unrolled Insertion Sort (Paolo Bonzini) : 75.30</li> </ul> <p><strong>Linux 64 bits, gcc 4.6.1 64 bits, Intel Core 2 Duo E8400, -O1</strong></p> <ul> <li>Direct call to qsort library function : 705.93</li> <li>Naive implementation (insertion sort) : 135.60</li> <li>Insertion Sort (Daniel Stutzbach) : 142.11</li> <li>Insertion Sort Unrolled : 126.75</li> <li>Rank Order : 46.42</li> <li>Rank Order with registers : 43.58</li> <li>Sorting Networks (Daniel Stutzbach) : 115.57</li> <li>Sorting Networks (Paul R) : 64.44</li> <li>Sorting Networks 12 with Fast Swap : 61.98</li> <li>Sorting Networks 12 reordered Swap : 54.67</li> <li>Sorting Networks 12 reordered Simple Swap : 31.54</li> <li>Reordered Sorting Network w/ fast swap : 31.24</li> <li>Reordered Sorting Network w/ fast swap V2 : 33.07</li> <li>Inlined Bubble Sort (Paolo Bonzini) : 45.79</li> <li>Unrolled Insertion Sort (Paolo Bonzini) : 80.15</li> </ul> <p>I included both -O1 and -O2 results because surprisingly for several programs O2 is <strong>less</strong> efficient than O1. I wonder what specific optimization has this effect ?</p> <h2><strong>Comments on proposed solutions</strong></h2> <p><strong>Insertion Sort (Daniel Stutzbach)</strong></p> <p>As expected minimizing branches is indeed a good idea.</p> <p><strong>Sorting Networks (Daniel Stutzbach)</strong></p> <p>Better than insertion sort. I wondered if the main effect was not get from avoiding the external loop. I gave it a try by unrolled insertion sort to check and indeed we get roughly the same figures (code is <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>).</p> <p><strong>Sorting Networks (Paul R)</strong></p> <p>The best so far. The actual code I used to test is <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>. Don't know yet why it is nearly two times as fast as the other sorting network implementation. Parameter passing ? Fast max ?</p> <p><strong>Sorting Networks 12 SWAP with Fast Swap</strong></p> <p>As suggested by Daniel Stutzbach, I combined his 12 swap sorting network with branchless fast swap (code is <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>). It is indeed faster, the best so far with a small margin (roughly 5%) as could be expected using 1 less swap. </p> <p>It is also interesting to notice that the branchless swap seems to be much (4 times) less efficient than the simple one using if on PPC architecture.</p> <p><strong>Calling Library qsort</strong></p> <p>To give another reference point I also tried as suggested to just call library qsort (code is <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>). As expected it is much slower : 10 to 30 times slower... as it became obvious with the new test suite, the main problem seems to be the initial load of the library after the first call, and it compares not so poorly with other version. It is just between 3 and 20 times slower on my Linux. On some architecture used for tests by others it seems even to be faster (I'm really surprised by that one, as library qsort use a more complex API).</p> <p><strong>Rank order</strong></p> <p>Rex Kerr proposed another completely different method : for each item of the array compute directly its final position. This is efficient because computing rank order do not need branch. The drawback of this method is that it takes three times the amount of memory of the array (one copy of array and variables to store rank orders). The performance results are very surprising (and interesting). On my reference architecture with 32 bits OS and Intel Core2 Quad E8300, cycle count was slightly below 1000 (like sorting networks with branching swap). But when compiled and executed on my 64 bits box (Intel Core2 Duo) it performed much better : it became the fastest so far. I finally found out the true reason. My 32bits box use gcc 4.4.1 and my 64bits box gcc 4.4.3 and the last one seems much better at optimising this particular code (there was very little difference for other proposals).</p> <p><em>update</em>:</p> <p>As published figures above shows this effect was still enhanced by later versions of gcc and Rank Order became consistently twice as fast as any other alternative.</p> <p><strong>Sorting Networks 12 with reordered Swap</strong></p> <p>The amazing efficiency of the Rex Kerr proposal with gcc 4.4.3 made me wonder : how could a program with 3 times as much memory usage be faster than branchless sorting networks? My hypothesis was that it had less dependencies of the kind read after write, allowing for better use of the superscalar instruction scheduler of the x86. That gave me an idea: reorder swaps to minimize read after write dependencies. More simply put: when you do <code>SWAP(1, 2); SWAP(0, 2);</code> you have to wait for the first swap to be finished before performing the second one because both access to a common memory cell. When you do <code>SWAP(1, 2); SWAP(4, 5);</code>the processor can execute both in parallel. I tried it and it works as expected, the sorting networks is running about 10% faster. </p> <p><strong>Sorting Networks 12 with Simple Swap</strong></p> <p>One year after the original post Steinar H. Gunderson suggested, that we should not try to outsmart the compiler and keep the swap code simple. It's indeed a good idea as the resulting code is about 40% faster! He also proposed a swap optimized by hand using x86 inline assembly code that can still spare some more cycles. The most surprising (it says volumes on programmer's psychology) is that one year ago none of used tried that version of swap. Code I used to test is <a href="http://pastebin.com/azzuk072" rel="noreferrer">here</a>. Others suggested other ways to write a C fast swap, but it yields the same performances as the simple one with a decent compiler.</p> <p>The "best" code is now as follow:</p> <pre><code>static inline void sort6_sorting_network_simple_swap(int * d){ #define min(x, y) (x&lt;y?x:y) #define max(x, y) (x&lt;y?y:x) #define SWAP(x,y) { const int a = min(d[x], d[y]); \ const int b = max(d[x], d[y]); \ d[x] = a; d[y] = b; } SWAP(1, 2); SWAP(4, 5); SWAP(0, 2); SWAP(3, 5); SWAP(0, 1); SWAP(3, 4); SWAP(1, 4); SWAP(0, 3); SWAP(2, 5); SWAP(1, 3); SWAP(2, 4); SWAP(2, 3); #undef SWAP #undef min #undef max } </code></pre> <p>If we believe our test set (and, yes it is quite poor, it's mere benefit is being short, simple and easy to understand what we are measuring), the average number of cycles of the resulting code for one sort is below 40 cycles (6 tests are executed). That put each swap at an average of 4 cycles. I call that amazingly fast. Any other improvements possible ?</p> </div> <p>转载于:https://stackoverflow.com/questions/2786899/fastest-sort-of-fixed-length-6-int-array</p>

PHP多维数组（或对象）到JSON_course

<div class="post-text" itemprop="text"> <p>I have 2 DB tables. table 2 is relational to table 1.</p> <p>In php I am building a multidimensional array to hold the data key/values.</p> <p>because PHP needs to have unique "keys" MY JSON is looking like this:</p> <pre><code>[ { "packs": { "9": { "characters": { "40": { "id": "40", "title": "Jack Bauer", "pic": "68bcbe014c.jpg", "gender": "Male" }, "41": { "id": "41", "title": "Chloe O'Brian", "pic": "ffb6acc8e3.jpg", "gender": "Male" }, "42": { "id": "42", "title": "Tony Almeida", "pic": "23f199e223.jpg", "gender": "Male" } } }, "7": { "characters": { "7": { "id": "7", "title": "Elvis Presley", "pic": "78300767ad.jpg", "gender": "Male" }, "16": { "id": "16", "title": "Madonna", "pic": "70663a42f7.jpg", "gender": "Male" }, "17": { "id": "17", "title": "Lady Gaga", "pic": "c5099c619b.jpg", "gender": "Male" }, "21": { "id": "21", "title": "Pink Floyd", "pic": "52ddce314a.jpg", "gender": "Male" }, "22": { "id": "22", "title": "Led Zeppelin", "pic": "84cd58ada3.jpg", "gender": "Male" }, "31": { "id": "31", "title": "The Beatles", "pic": "bd22a4d648.jpg", "gender": "Male" }, "32": { "id": "32", "title": "Foo Fighters", "pic": "250fb6ecec.jpg", "gender": "Male" }, "33": { "id": "33", "title": "Bananarama", "pic": "da7c2b56cf.jpg", "gender": "Male" }, "35": { "id": "35", "title": "Boney-M", "pic": "3cbdada38b.jpg", "gender": "Male" }, "38": { "id": "38", "title": "The Spice Girls", "pic": "4751f0fbb7.jpeg", "gender": "Male" }, "39": { "id": "39", "title": "Girls Aloud", "pic": "644dcf71ca.jpg", "gender": "Male" } } }, "8": { "characters": { "9": { "id": "9", "title": "Keith Lemon", "pic": "ff6ef10853.jpg.jpg", "gender": "Male" }, "23": { "id": "23", "title": "Fearne Cotton", "pic": "0d038b6516.jpg", "gender": "Male" }, "24": { "id": "24", "title": "Holly Willoughby", "pic": "836fc4184c.jpg", "gender": "Male" }, "30": { "id": "30", "title": "Rufus Hound", "pic": "062bee9602.jpg", "gender": "Male" } } }, "3": { "characters": { "5": { "id": "5", "title": "Tom Cruise", "pic": "ff296fafb9.jpg", "gender": "Male" }, "10": { "id": "10", "title": "Linda Lovelace", "pic": "ac1bea43d3.jpg", "gender": "Male" }, "15": { "id": "15", "title": "Gwyneth Paltrow", "pic": "43a22d7240.jpg", "gender": "Male" }, "44": { "id": "44", "title": "Errol Flynn", "pic": "cea17c1275.jpg", "gender": "Male" }, "45": { "id": "45", "title": "Halle Berry", "pic": "752b5c92c5.jpg", "gender": "Male" } } }, "2": { "characters": { "4": { "id": "4", "title": "Donald Duck", "pic": "8d367f41b1.jpg", "gender": "Male" }, "6": { "id": "6", "title": "Mickey Mouse", "pic": "8d9629c115.jpg", "gender": "Male" }, "28": { "id": "28", "title": "Pluto", "pic": "fb2c0e2dd0.jpg", "gender": "Male" }, "29": { "id": "29", "title": "Minnie Mouse", "pic": "378760ff77.jpg", "gender": "Male" }, "36": { "id": "36", "title": "Cinderella", "pic": "a7e4888213.jpg", "gender": "Male" }, "37": { "id": "37", "title": "Snow White", "pic": "a9cf05a857.jpg", "gender": "Male" } } }, "4": { "characters": { "3": { "id": "3", "title": "Bill Clinton", "pic": "03c6567ddb.jpg", "gender": "Male" }, "11": { "id": "11", "title": "Margaret Thatcher", "pic": "91c9fa9fd0.jpg", "gender": "Male" }, "13": { "id": "13", "title": "David Cameron", "pic": "a689984360.jpg", "gender": "Male" }, "14": { "id": "14", "title": "Nick Clegg", "pic": "3243e298e5.jpg", "gender": "Male" }, "26": { "id": "26", "title": "George Bush JR", "pic": "46296f6b0e.jpg", "gender": "Male" }, "27": { "id": "27", "title": "Ed Milliband", "pic": "66f1449994.jpg", "gender": "Male" } } }, "5": { "characters": { "8": { "id": "8", "title": "Stephen Hawking", "pic": "b8c4f17530.jpg", "gender": "Male" }, "18": { "id": "18", "title": "Alan Turing", "pic": "82b4d84e35.jpg", "gender": "Male" }, "19": { "id": "19", "title": "Albert Einstein", "pic": "a6cd74dbaa.jpg", "gender": "Male" }, "34": { "id": "34", "title": "Brian Cox (prof)", "pic": "92b6005de9.jpg", "gender": "Male" }, "43": { "id": "43", "title": "Richard Feynman", "pic": "5de10d1128.jpg", "gender": "Male" } } }, "6": { "characters": { "12": { "id": "12", "title": "Jeff Koons", "pic": "8e3ca5f497.jpg", "gender": "Male" }, "20": { "id": "20", "title": "Salvador Dali", "pic": "b5bafb7934.jpg", "gender": "Male" }, "25": { "id": "25", "title": "Rembrandt", "pic": "73e2710029.jpg", "gender": "Male" }, "49": { "id": "49", "title": "Vincent Van Gough", "pic": "6ee455ab28.jpg", "gender": "Male" } } } } } </code></pre> <p>]</p> <p>I am trying to solve a problem that my iOS dev wants sorting... apparently the "{"packs":{"9": " 9 is wrong and does not follow the key:value JSON structure. How on earth do I create a correct PHP array or object for that matter with the unique identifier for each of the result sets from DB table 1?</p> <p>the result should be structured like this:</p> <p>data_db_1:1</p> <p>data_db_2:id data_db_2:title data_db_2:pic data_db_2:gender</p> <p>data_db_1:2</p> <p>data_db_2:id data_db_2:title data_db_2:pic data_db_2:gender</p> <p>data_db_1:3</p> <p>data_db_2:id data_db_2:title data_db_2:pic data_db_2:gender</p> <p>data_db_1:4 data_db_2:id data_db_2:title data_db_2:pic data_db_2:gender</p> <p>and look like this:</p> <pre><code> { "id": "9", "title": "24", "credits": "100", "character": [ { "id": "50", "title": "Jack Bauer", "pic": "68bcbe014c.jpg", "gender": "Male" }, { "id": "50", "title": "Jack Bauer", "pic": "68bcbe014c.jpg", "gender": "Male" }, { "id": "50", "title": "Jack Bauer", "pic": "68bcbe014c.jpg", "gender": "Male" }, { "id": "50", "title": "Jack Bauer", "pic": "68bcbe014c.jpg", "gender": "Male" } ] </code></pre> <p>}</p> <p>I cant find allot on the web relating to this. The only way I can think to solve it is to create each part seperately from PHP arrays using json_encode() and echo and a mess of concat. Surely json_encode() should be capable of creating correct JSON from a simple php array, a complex php multidimensional array or a PHP object without breaking a sweat???</p> <hr> <p>my php function to do this as requested:</p> <pre><code>$data_ar = output_pack_data($pack_id); echo "[".json_encode($data_ar)."]"; // first bit of dirty here function output_pack_data($pack_id = false) { global $db; $output_keys = true; //false; if($pack_id != false) { $q = "WHERE id='{$pack_id}' AND active = '1'"; // select the relevant pack ID } else { $q = "WHERE active='1' ORDER BY order_num ASC"; // select all pack ids } $rs = $db-&gt;rs("whoami_packs",$q); $pack_obj = new stdClass(); // declare new std class object here...... $data = array(); // prep new array to hold the data while($rs &amp;&amp; $r = $db-&gt;fetch($rs)) // loop thorugh each pack id { $pack_obj-&gt;packs-&gt;id = $r-&gt;id; // add the pack title $pack_obj-&gt;packs-&gt;title = $r-&gt;title; // add the pack title $pack_obj-&gt;packs-&gt;credits = $r-&gt;credits; // add the required credits to access $packs_rs = $db-&gt;rs("whoami_characters","WHERE pack_id='{$r-&gt;id}' AND active = '1'"); // get the character data relevant for this pack $i=0; while($packs_rs &amp;&amp; $pack_r = $db-&gt;fetch($packs_rs)) // loop through the character data { $id = $r-&gt;id; if($output_keys == false) { $data['packs'][$r-&gt;id]['characters'][$pack_r-&gt;id][$pack_r-&gt;title][$pack_r-&gt;pic][$pack_r-&gt;gender] = true; // build the array } else { $data['packs'][$r-&gt;id]['characters'][$pack_r-&gt;id]['id'] = $pack_r-&gt;id; // build the array $data['packs'][$r-&gt;id]['characters'][$pack_r-&gt;id]['title'] = str_out($pack_r-&gt;title); // build the array $data['packs'][$r-&gt;id]['characters'][$pack_r-&gt;id]['pic'] = $pack_r-&gt;pic; $data['packs'][$r-&gt;id]['characters'][$pack_r-&gt;id]['gender'] = ($pack_r-&gt;gender = 'm') ? "Male" : "Female"; } } } return $data; // return the array </code></pre> <p>}</p> </div>

如何在PHP中将这个复杂的文本块解析为多维数组？_course

<div class="post-text" itemprop="text"> <p>I have a <strong>complex</strong> text-block; and, its content is:</p> <pre> line_1(element_1,sub_line_1(sub_element_1,sub_element_2),element_2). line_2(sub_line_2(element_3,element_4),sub_line_3(sub_sub_line(element_5,element_6),element_7),element_8). ... line_n(element_a,element_b,element_c).</pre> <p>And, there is already an simple array, in PHP code:</p> <pre><code>$my_array = array(); </code></pre> <p>Now, I want to parse into this PHP array, like:</p> <pre><code>$my_array = array ( "line_1" =&gt; array ( "element_1", "sub_line_1" =&gt; array ( "sub_element_1", "sub_element_2" ), "element_2"), "line_2" =&gt; array ( "sub_line_2" =&gt; array ( "sub_element_3", "sub_element_4" ), "sub_line_3" =&gt; array ( "sub_sub_line" =&gt; array ("element_5","element_6"), "sub_element_7" ), "element_8" ) ), ... "line_n" =&gt; array ("element_a", "element_b", "element_c") ); </code></pre> <p>All data is <strong>general</strong>; and, the <strong>level</strong> of array is <strong>more</strong>. Could you help me to do it, with PHP?</p> </div>