C++ multiple definition of ....问题

header
cpp
main
C++小白一枚,照着教科书和视频完全一样的编了,查了试了所有的方法依然无法解决,
myvector的cpp里边所有函数都说重复定义。。有大侠愿意出手相助一下吗?不胜感激!

c++

3个回答

看下是不是头文件重复包含造成的。

提供如下方法:
给自己写的引用了的头文件加上条件编译

#ifndef _MyVector_H
#define _MyVector_H
#endif 

或者将上面的两个方法合并,你因为加了两个#include "myvector.h"(后两个文件里面都加了相同的头文件)

看上去没什么问题
给你几个建议吧:
1. 清理一下,重新编译
2. 把文件名跟类名统一一下
3. 根据报错,查找两个重复定义的包含路径, 分别看看这两个包含路径是怎么回事。

Csdn user default icon
上传中...
上传图片
插入图片
抄袭、复制答案,以达到刷声望分或其他目的的行为,在CSDN问答是严格禁止的,一经发现立刻封号。是时候展现真正的技术了!
其他相关推荐
C++ multiple definition of ....问题

![header](https://img-ask.csdn.net/upload/201710/31/1509462000_105043.png) ![cpp](https://img-ask.csdn.net/upload/201710/31/1509462084_532334.png) ![main](https://img-ask.csdn.net/upload/201710/31/1509462038_60249.png) C++小白一枚,照着教科书和视频完全一样的编了,查了试了所有的方法依然无法解决, myvector的cpp里边所有函数都说重复定义。。有大侠愿意出手相助一下吗?不胜感激!

mapoutput.c:(.data+0x0): multiple definition of `p',这个问题怎么解决啊?

我这个蔡鸡初学者在尝试写一个推箱子的程序,但是今天编译的时候遇到了标题所显示的问题.了一下,是'p'这个指针被多次声明,但是我检查了很多遍(很有可能我太菜.......),应该不会有什么被多次声明什么的,但是它确实......,希望大家帮我康康(编译器用的是DEV c++) 附上代码 main,c ``` #include <stdio.h> #include "maps.h" #include "head.h" int main() { player.a=1; player.b=8; int x=0,y=0,level=114514,z=0; change:scanf_s("%d",&level); level--; system("cls"); while(z==0){ mapoutput(x,y,level,map); int mov; scanf_s("%d",&mov); move(mov,level,map,&player); system("cls"); z=judgement(level,map); if(z==1){ z=0; goto change; } } return 0; } ``` move.c(太多了,省略一些,如果需要的话我在发出来,实在不行我发源文件) ``` #include <stdio.h> #include "head.h" #include "maps.h" void move(int mov,int level,int map[2][6][10],struct post *p){ .............. } ``` judgement.c(同上) ``` #include <stdio.h> #include "head.h" #include "maps.h" int judgement(int level,int map[2][6][10]){ ........... return z; } ``` 然后是两个头文件 map.h ``` #ifndef LIST_HEAD2 #define LIST_HEAD2 int map[2][6][10]={ ........ }; #endif ``` head.h(感觉问题出在这里,但是....) ``` #ifndef LIST_HEAD1 #define LIST_HEAD1 struct post { int x; int y; }player; struct post *p=&player; void mapoutput(int x,int y,int level,int map[2][6][10]); void move(int mov,int level,int map[2][6][10],struct post *p); int judgement(int level,int map[2][6][10]); #endif ``` 然后是运行的报错 ![图片说明](https://img-ask.csdn.net/upload/202002/12/1581489321_528436.png) 希望大佬们能帮我看看问题出在哪里了 //救救孩子,秋梨膏

关于‘multiple definition of 'main'’的一点疑问

我在Dev-C++里建立了一个项目:Peach; 之后又新建了两个源代码文件; 1、Peach.c #include <stdio.h> int main() { int i=0,sum=1; for(i=1;i<=9;i++) { sum=(sum+1)*2; } printf("SUM=%d\n",sum); return 0; } 2、Peach_My.c #include <stdio.h> int main() { int SUM,i,sum; sum=SUM; for(i=1;i<=9;i++) { sum=sum/2-1; } if(sum=1) { printf("SUM=%d\n",SUM); } return 0; } 运行时老是出现这个问题: multiple definition of 'main' 不知道为什么?

使用CLion遇到的问题 multiple definition of `main' ld returned 1 exit status

![图片说明](https://img-ask.csdn.net/upload/202001/09/1578585095_670327.png) [ 33%] Linking CXX executable untitled.exe CMakeFiles\untitled.dir/objects.a(test.cpp.obj): In function `main': C:/Users/Lee/CLionProjects/untitled/test.cpp:2: multiple definition of `main' CMakeFiles\untitled.dir/objects.a(main.cpp.obj):C:/Users/Lee/CLionProjects/untitled/main.cpp:3: first defined here collect2.exe: error: ld returned 1 exit status mingw32-make.exe[3]: *** [CMakeFiles\untitled.dir\build.make:100: untitled.exe] Error 1 mingw32-make.exe[2]: *** [CMakeFiles\Makefile2:75: CMakeFiles/untitled.dir/all] Error 2 mingw32-make.exe[1]: *** [CMakeFiles\Makefile2:82: CMakeFiles/untitled.dir/rule] Error 2 mingw32-make.exe: *** [Makefile:117: untitled] Error 2 最开始是Cmake有问题 用大佬帖子里的方法改了系统文件夹名字之后好了 然鹅 不知道是什么情况 麻烦大佬们帮忙看看

新手求大神指教qt中error: multiple definition of用网上查的方法还是报错

在做的是一个学生管理系统 我用了一个头文件把所有全局变量放了进去 ![图片说明](https://img-ask.csdn.net/upload/201807/27/1532683535_128891.png) 然后双击报错那里出现的界面是这个 但并没有students的定义啊 ![图片说明](https://img-ask.csdn.net/upload/201807/27/1532683668_618570.png) 是不是下面两个文件中对students 里的值都有定义所以导致报错?那应该怎样修改呢? ![图片说明](https://img-ask.csdn.net/upload/201807/27/1532683901_597476.png) ![图片说明](https://img-ask.csdn.net/upload/201807/27/1532683910_917481.png)

openssl和mysql冲突 ERR_remove_thread_state

openssl版本:openssl-1.1.0k mysql版本:mysql-5.7.27 静态库,编译报如下错误: /thirdparty/mysql/lib/libmysqlclient.a(ssl.cpp.o): In function `ERR_remove_thread_state': /export/home/pb2/build/sb_0-34537258-1560179931.8/mysql-5.7.27/extra/yassl/src/ssl.cpp:1619: multiple definition of `ERR_remove_thread_state' /home/lics/code/transfer/thirdparty/openssl/lib/libcrypto.a(err.o):err.c:(.text+0xb60): first defined here collect2: error: ld returned 1 exit status make[1]: [build] Error 1 (ignored) 请问有谁遇到过吗?

关于c++类的静态变量的编译出现重复定义

../Manager.o:(.data+0x0): multiple definition of `Cdebug::n' /tmp/ccm2hcIk.o:(.data+0x0): first defined here ../Epoller.o:(.data+0x0): multiple definition of `Cdebug::n' /tmp/ccm2hcIk.o:(.data+0x0): first defined here collect2: error: ld returned 1 exit status Cdebug的源码如下: #ifndef DEBUG_H #define DEBUG_H class Cdebug{ ..... private: static int n; } int Cdebug::n=1; #endif 这里我已经用#ifndef 防止头文件重复导入,为什么还会出错?

数据结构里的AVL树的计算的问题,怎么才能利用C语言程序的过程来实现编写

Problem Description An AVL tree is a kind of balanced binary search tree. Named after their inventors, Adelson-Velskii and Landis, they were the first dynamically balanced trees to be proposed. Like red-black trees, they are not perfectly balanced, but pairs of sub-trees differ in height by at most 1, maintaining an O(logn) search time. Addition and deletion operations also take O(logn) time. Definition of an AVL tree An AVL tree is a binary search tree which has the following properties: 1. The sub-trees of every node differ in height by at most one. 2. Every sub-tree is an AVL tree. Balance requirement for an AVL tree: the left and right sub-trees differ by at most 1 in height.An AVL tree of n nodes can have different height. For example, n = 7: So the maximal height of the AVL Tree with 7 nodes is 3. Given n,the number of vertices, you are to calculate the maximal hight of the AVL tree with n nodes. Input Input file contains multiple test cases. Each line of the input is an integer n(0<n<=10^9). A line with a zero ends the input. Output An integer each line representing the maximal height of the AVL tree with n nodes. Sample Input 1 2 0 Sample Output 0 1

Occurrence

Given a string A which can be represented as A1A2..An (n is the length of A) and a string B which can be represented as B1B2..Bm (m is the length of B), you will need to find the occurrence of B from A. The definition of occurrence is as follows: If there exists an index p (p >= 1 and p + m <= n), and ApAp+1..Ap+m-1 matches with any rotation of B (B1B2..Bm-1Bm, B2B3..BmB1, ��, BmB1..Bm-2Bm-1 are all the rotation of B), we call it is an occurrence of B from A. Input: This problem contains multiple test cases. Each test case contains two lines, which are the strings A and B. The length of A is not greater then 1000 and the length of B is not greater than 100. All the strings are only consist of lowercase letters. Output: Each test should output an integer indicating the occurrence of B from A in a single line. Sample Input: abab ab aaaa a aaaa aa Sample Output: 3 4 3

二叉平衡树的高效率的求法的问题,运用C语言系统的编程的技术

Problem Description An AVL tree is a kind of balanced binary search tree. Named after their inventors, Adelson-Velskii and Landis, they were the first dynamically balanced trees to be proposed. Like red-black trees, they are not perfectly balanced, but pairs of sub-trees differ in height by at most 1, maintaining an O(logn) search time. Addition and deletion operations also take O(logn) time. Definition of an AVL tree An AVL tree is a binary search tree which has the following properties: 1. The sub-trees of every node differ in height by at most one. 2. Every sub-tree is an AVL tree. Balance requirement for an AVL tree: the left and right sub-trees differ by at most 1 in height.An AVL tree of n nodes can have different height. For example, n = 7: So the maximal height of the AVL Tree with 7 nodes is 3. Given n,the number of vertices, you are to calculate the maximal hight of the AVL tree with n nodes. Input Input file contains multiple test cases. Each line of the input is an integer n(0<n<=10^9). A line with a zero ends the input. Output An integer each line representing the maximal height of the AVL tree with n nodes. Sample Input 1 2 0 Sample Output 0 1

错误的曲线的标注问题,怎么使用C语言的程序的编写过程的方式有效实现的代码怎么写

Problem Description Josephina is a clever girl and addicted to Machine Learning recently. She pays much attention to a method called Linear Discriminant Analysis, which has many interesting properties. In order to test the algorithm's efficiency, she collects many datasets. What's more, each data is divided into two parts: training data and test data. She gets the parameters of the model on training data and test the model on test data. To her surprise, she finds each dataset's test error curve is just a parabolic curve. A parabolic curve corresponds to a quadratic function. In mathematics, a quadratic function is a polynomial function of the form f(x) = ax2 + bx + c. The quadratic will degrade to linear function if a = 0. It's very easy to calculate the minimal error if there is only one test error curve. However, there are several datasets, which means Josephina will obtain many parabolic curves. Josephina wants to get the tuned parameters that make the best performance on all datasets. So she should take all error curves into account, i.e., she has to deal with many quadric functions and make a new error definition to represent the total error. Now, she focuses on the following new function's minimum which related to multiple quadric functions. The new function F(x) is defined as follows: F(x) = max(Si(x)), i = 1...n. The domain of x is [0, 1000]. Si(x) is a quadric function. Josephina wonders the minimum of F(x). Unfortunately, it's too hard for her to solve this problem. As a super programmer, can you help her? Input The input contains multiple test cases. The first line is the number of cases T (T < 100). Each case begins with a number n (n ≤ 10000). Following n lines, each line contains three integers a (0 ≤ a ≤ 100), b (|b| ≤ 5000), c (|c| ≤ 5000), which mean the corresponding coefficients of a quadratic function. Output For each test case, output the answer in a line. Round to 4 digits after the decimal point. Sample Input 2 1 2 0 0 2 2 0 0 2 -4 2 Sample Output 0.0000 0.5000

GCJ 使用出现一堆故障,但我不知道问题出在哪里

我在使用MinGW的GCJ时,出现了一堆故障: > gcj -c Greeting.java -o Greeting.o [这一步正常] > gcj --main=Greeting -o Greeting.exe Greeting.o C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../libgcj.a(win32.o):win32.cc:(.data+0x0): multiple definition of `_CRT_MT' C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../libmingw32.a(crtst.o):(.bss+0x0): first defined here C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../libmingw32.a(setargv.o):(.text+0x33): undefined reference to `__chkstk_ms' C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../libmingwex.a(glob.o):(.text+0x6d2): undefined reference to `__chkstk_ms' C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../libmingwex.a(glob.o):(.text+0x8b8): undefined reference to `__chkstk_ms' C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../libmingwex.a(glob.o):(.text+0x900): undefined reference to `__chkstk_ms' C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../libmingwex.a(glob.o):(.text+0xa25): undefined reference to `__chkstk_ms' C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../libmingwex.a(glob.o):(.text+0xc15): more undefined references to `__chkstk_ms' follow collect2: ld returned 1 exit status 这到底什么情况啊?

VsCode Go扩展程序调试Example_c.c文件而不是实际文件

<div class="post-text" itemprop="text"> <p>I just tried to execute a Hello World from VSCode 1.28.2 (Windows 8.1) in a C:\Scripts\hello_world.go file:</p> <pre><code>package main import ( "fmt" ) func main() { fmt.Println("Hello, Gopher!") } </code></pre> <p>My environment is as follows:</p> <ul> <li>I installed Go from scratch using the Windows installer:</li> </ul> <blockquote> <pre><code>$ go version go version go1.11.2 windows/amd64 </code></pre> </blockquote> <ul> <li>Installed on C:\Go</li> <li>Installed VSCode Go Extension: <a href="https://marketplace.visualstudio.com/items?itemName=ms-vscode.Go" rel="nofollow noreferrer">https://marketplace.visualstudio.com/items?itemName=ms-vscode.Go</a></li> <li>Installed debugger: </li> </ul> <blockquote> <p>go get -u github.com/derekparker/delve/cmd/dlv</p> </blockquote> <ul> <li>Checked with SystemPropertiesAdvanced: <ul> <li>Local Variable GOPATH = %USERPROFILE%\go</li> <li>Local Variable PATH adds %USERPROFILE%\go\bin</li> <li>System Variable PATH adds C:\Go\bin</li> <li>System Variable GOROOT = C:\Go\</li> </ul></li> <li>I have MinGW64, GitBash and MinGW 1.0 (However I don't see how that could affect running Go from VSCode)</li> <li>Running from cmd.exe runs the program without problems at all:</li> </ul> <blockquote> <pre><code>C:\Scripts&gt;go run hello_world.go Hello, Gopher! </code></pre> </blockquote> <p>In VSCode settings my global go.gopath and go.goroot settings are:</p> <pre><code> // Specify GOPATH here to override the one that is set as environment variable. The inferred GOPATH from workspace root overrides this, if go.inferGopath is set to true. "go.gopath": null // Specifies the GOROOT to use when no environment variable is set. "go.goroot": null </code></pre> <p>So I customized the variables from VSCode as follows:</p> <pre><code>{ "editor.renderControlCharacters": false, "go.inferGopath": true, "go.goroot": "C:\\go", } </code></pre> <p>Now this is the weird part. When I hit Ctrl+F5 compilation takes a "Example_c.c" file (?) and reports errors with that file (which I never created or even knew that existed):</p> <pre><code># _/c_/Scripts C:\Users\Mike\AppData\Local\Temp\go-build530760830\b001\_x003.o: In function `main': ./Example_c.c:1: multiple definition of `main' C:\Users\Mike\AppData\Local\Temp\go-build530760830\b001\_cgo_main.o:/tmp/go-build/_cgo_main.c:1: first defined here C:\Users\Mike\AppData\Local\Temp\go-build530760830\b001\_x004.o: In function `main': ./Test_C-01.c:3: multiple definition of `main' C:\Users\Mike\AppData\Local\Temp\go-build530760830\b001\_cgo_main.o:/tmp/go-build/_cgo_main.c:1: first defined here C:\Users\Mike\AppData\Local\Temp\go-build530760830\b001\_x005.o: In function `main': ./Test_C-02.c:3: multiple definition of `main' C:\Users\Mike\AppData\Local\Temp\go-build530760830\b001\_cgo_main.o:/tmp/go-build/_cgo_main.c:1: first defined here collect2: ld returned 1 exit status # _/c_/Scripts Example_c.c: In function 'main': Example_c.c:2:3: warning: incompatible implicit declaration of built-in function 'printf' Example_c.c:4:19: warning: incompatible implicit declaration of built-in function 'malloc' Example_c.c:9:3: warning: incompatible implicit declaration of built-in function 'free' exit status 2 Process exiting with code: 1 </code></pre> <p>I already tried deleting all my temporary files and restarted VsCode multiple times. The whole experience to setup a Go environment to debug a hello world is really dissapointing. </p> <p>What else can I check? Any hints?</p> </div>

AVL数据结构上的平衡树的高度的计算方式,怎么采用C语言的办法对这个问题的实现?

Problem Description An AVL tree is a kind of balanced binary search tree. Named after their inventors, Adelson-Velskii and Landis, they were the first dynamically balanced trees to be proposed. Like red-black trees, they are not perfectly balanced, but pairs of sub-trees differ in height by at most 1, maintaining an O(logn) search time. Addition and deletion operations also take O(logn) time. Definition of an AVL tree An AVL tree is a binary search tree which has the following properties: 1. The sub-trees of every node differ in height by at most one. 2. Every sub-tree is an AVL tree. Balance requirement for an AVL tree: the left and right sub-trees differ by at most 1 in height.An AVL tree of n nodes can have different height. For example, n = 7: So the maximal height of the AVL Tree with 7 nodes is 3. Given n,the number of vertices, you are to calculate the maximal hight of the AVL tree with n nodes. Input Input file contains multiple test cases. Each line of the input is an integer n(0<n<=10^9). A line with a zero ends the input. Output An integer each line representing the maximal height of the AVL tree with n nodes. Sample Input 1 2 0 Sample Output 0 1

用C接口构建Got +

<div class="post-text" itemprop="text"> <p>I'm trying to build a Go programm which uses external C code as an interface for Gtk+.</p> <p>That's the basic Go code I've got (ui.h.go):</p> <pre><code>package main //#cgo pkg-config: gtk+-3.0 //#include "ui.h" import "C" func CInit() { C.Init(nil, 0) } func CMain() { C.Main() } func CShowWindow() { C.ShowWindow() } func main() { CInit() CShowWindow() CMain() } </code></pre> <p>C code is compiled from vala into an object file (ui.o) and a header file (ui.h):</p> <pre><code>#ifndef __UI_H__ #define __UI_H__ #include &lt;glib.h&gt; #include &lt;stdlib.h&gt; #include &lt;string.h&gt; G_BEGIN_DECLS void ShowWindow (void); void Init (gchar** args, int args_length1); void Main (void); G_END_DECLS #endif </code></pre> <p>When I try <code>go build ui.h.go</code> I get:</p> <pre><code># command-line-arguments /tmp/go-build916459533/command-line-arguments/_obj/ui.h.cgo2.o: In function `_cgo_80fc53cbf347_Cfunc_Init': ./ui.h.go:37: undefined reference to `Init' /tmp/go-build916459533/command-line-arguments/_obj/ui.h.cgo2.o: In function `_cgo_80fc53cbf347_Cfunc_Main': ./ui.h.go:46: undefined reference to `Main' /tmp/go-build916459533/command-line-arguments/_obj/ui.h.cgo2.o: In function `_cgo_80fc53cbf347_Cfunc_ShowWindow': ./ui.h.go:55: undefined reference to `ShowWindow' collect2: error: ld returned 1 exit status </code></pre> <p>Which is logical, I haven't provided my object file. But if I specify it in cgo header of <code>ui.h.go</code> like that...</p> <pre><code>//#cgo LDFLAGS: ui.o //#cgo pkg-config: gtk+-3.0 //#include "ui.h" import "C" </code></pre> <p>I get multiple definition error, as if it's being linked twice.</p> <pre><code># command-line-arguments /usr/local/go/pkg/tool/linux_amd64/link: running gcc failed: exit status 1 ui.o:(.bss+0x0): multiple definition of `window' /tmp/go-link-461834384/000000.o:/home/oleg/Документы/Projects/rasp/ui.h.go:38: first defined here ui.o: In function `ShowWindow': ui.c:(.text+0x0): multiple definition of `ShowWindow' /tmp/go-link-461834384/000000.o:(.text+0x25): first defined here ui.o: In function `Init': ui.c:(.text+0x29): multiple definition of `Init' /tmp/go-link-461834384/000000.o:(.text+0x4e): first defined here ui.o: In function `Main': ui.c:(.text+0x116): multiple definition of `Main' /tmp/go-link-461834384/000000.o:(.text+0x13b): first defined here collect2: error: ld returned 1 exit status </code></pre> <p>How do I link my ui.o file to the Go program correctly? Thank you.</p> </div>

Error Curves 错误曲线的问题

Problem Description Josephina is a clever girl and addicted to Machine Learning recently. She pays much attention to a method called Linear Discriminant Analysis, which has many interesting properties. In order to test the algorithm's efficiency, she collects many datasets. What's more, each data is divided into two parts: training data and test data. She gets the parameters of the model on training data and test the model on test data. To her surprise, she finds each dataset's test error curve is just a parabolic curve. A parabolic curve corresponds to a quadratic function. In mathematics, a quadratic function is a polynomial function of the form f(x) = ax2 + bx + c. The quadratic will degrade to linear function if a = 0. It's very easy to calculate the minimal error if there is only one test error curve. However, there are several datasets, which means Josephina will obtain many parabolic curves. Josephina wants to get the tuned parameters that make the best performance on all datasets. So she should take all error curves into account, i.e., she has to deal with many quadric functions and make a new error definition to represent the total error. Now, she focuses on the following new function's minimum which related to multiple quadric functions. The new function F(x) is defined as follows: F(x) = max(Si(x)), i = 1...n. The domain of x is [0, 1000]. Si(x) is a quadric function. Josephina wonders the minimum of F(x). Unfortunately, it's too hard for her to solve this problem. As a super programmer, can you help her? Input The input contains multiple test cases. The first line is the number of cases T (T < 100). Each case begins with a number n (n ≤ 10000). Following n lines, each line contains three integers a (0 ≤ a ≤ 100), b (|b| ≤ 5000), c (|c| ≤ 5000), which mean the corresponding coefficients of a quadratic function. Output For each test case, output the answer in a line. Round to 4 digits after the decimal point. Sample Input 2 1 2 0 0 2 2 0 0 2 -4 2 Sample Output 0.0000 0.5000

Error Curves

Description Josephina is a clever girl and addicted to Machine Learning recently. She pays much attention to a method called Linear Discriminant Analysis, which has many interesting properties. In order to test the algorithm's efficiency, she collects many datasets. What's more, each data is divided into two parts: training data and test data. She gets the parameters of the model on training data and test the model on test data. To her surprise, she finds each dataset's test error curve is just a parabolic curve. A parabolic curve corresponds to a quadratic function. In mathematics, a quadratic function is a polynomial function of the form f(x) = ax2 + bx + c. The quadratic will degrade to linear function if a = 0. It's very easy to calculate the minimal error if there is only one test error curve. However, there are several datasets, which means Josephina will obtain many parabolic curves. Josephina wants to get the tuned parameters that make the best performance on all datasets. So she should take all error curves into account, i.e., she has to deal with many quadric functions and make a new error definition to represent the total error. Now, she focuses on the following new function's minimum which related to multiple quadric functions. The new function F(x) is defined as follows: F(x) = max(Si(x)), i = 1...n. The domain of x is [0, 1000]. Si(x) is a quadric function. Josephina wonders the minimum of F(x). Unfortunately, it's too hard for her to solve this problem. As a super programmer, can you help her? Input The input contains multiple test cases. The first line is the number of cases T (T < 100). Each case begins with a number n (n ≤ 10000). Following n lines, each line contains three integers a (0 ≤ a ≤ 100), b (|b| ≤ 5000), c (|c| ≤ 5000), which mean the corresponding coefficients of a quadratic function. Output For each test case, output the answer in a line. Round to 4 digits after the decimal point. Sample Input 2 1 2 0 0 2 2 0 0 2 -4 2 Sample Output 0.0000 0.5000

Error Curves 错误的曲线

Problem Description Josephina is a clever girl and addicted to Machine Learning recently. She pays much attention to a method called Linear Discriminant Analysis, which has many interesting properties. In order to test the algorithm's efficiency, she collects many datasets. What's more, each data is divided into two parts: training data and test data. She gets the parameters of the model on training data and test the model on test data. To her surprise, she finds each dataset's test error curve is just a parabolic curve. A parabolic curve corresponds to a quadratic function. In mathematics, a quadratic function is a polynomial function of the form f(x) = ax2 + bx + c. The quadratic will degrade to linear function if a = 0. It's very easy to calculate the minimal error if there is only one test error curve. However, there are several datasets, which means Josephina will obtain many parabolic curves. Josephina wants to get the tuned parameters that make the best performance on all datasets. So she should take all error curves into account, i.e., she has to deal with many quadric functions and make a new error definition to represent the total error. Now, she focuses on the following new function's minimum which related to multiple quadric functions. The new function F(x) is defined as follows: F(x) = max(Si(x)), i = 1...n. The domain of x is [0, 1000]. Si(x) is a quadric function. Josephina wonders the minimum of F(x). Unfortunately, it's too hard for her to solve this problem. As a super programmer, can you help her? Input The input contains multiple test cases. The first line is the number of cases T (T < 100). Each case begins with a number n (n ≤ 10000). Following n lines, each line contains three integers a (0 ≤ a ≤ 100), b (|b| ≤ 5000), c (|c| ≤ 5000), which mean the corresponding coefficients of a quadratic function. Output For each test case, output the answer in a line. Round to 4 digits after the decimal point. Sample Input 2 1 2 0 0 2 2 0 0 2 -4 2 Sample Output 0.0000 0.5000

大学四年自学走来,这些私藏的实用工具/学习网站我贡献出来了

大学四年,看课本是不可能一直看课本的了,对于学习,特别是自学,善于搜索网上的一些资源来辅助,还是非常有必要的,下面我就把这几年私藏的各种资源,网站贡献出来给你们。主要有:电子书搜索、实用工具、在线视频学习网站、非视频学习网站、软件下载、面试/求职必备网站。 注意:文中提到的所有资源,文末我都给你整理好了,你们只管拿去,如果觉得不错,转发、分享就是最大的支持了。 一、电子书搜索 对于大部分程序员...

在中国程序员是青春饭吗?

今年,我也32了 ,为了不给大家误导,咨询了猎头、圈内好友,以及年过35岁的几位老程序员……舍了老脸去揭人家伤疤……希望能给大家以帮助,记得帮我点赞哦。 目录: 你以为的人生 一次又一次的伤害 猎头界的真相 如何应对互联网行业的「中年危机」 一、你以为的人生 刚入行时,拿着傲人的工资,想着好好干,以为我们的人生是这样的: 等真到了那一天,你会发现,你的人生很可能是这样的: ...

程序员请照顾好自己,周末病魔差点一套带走我。

程序员在一个周末的时间,得了重病,差点当场去世,还好及时挽救回来了。

ArrayList源码分析(入门篇)

ArrayList源码分析 前言: 写这篇博客的主要原因是,在我上一次参加千牵科技Java实习生面试时,有被面试官问到ArrayList为什么查找的速度较快,插入和删除的速度较慢?当时我回答得不好,很大的一部分原因是因为我没有阅读过ArrayList源码,虽然最后收到Offer了,但我拒绝了,打算寒假学得再深入些再广泛些,下学期开学后再去投递其他更好的公司。为了更加深入理解ArrayList,也为

我以为我学懂了数据结构,直到看了这个导图才发现,我错了

数据结构与算法思维导图

String s = new String(" a ") 到底产生几个对象?

老生常谈的一个梗,到2020了还在争论,你们一天天的,哎哎哎,我不是针对你一个,我是说在座的各位都是人才! 上图红色的这3个箭头,对于通过new产生一个字符串(”宜春”)时,会先去常量池中查找是否已经有了”宜春”对象,如果没有则在常量池中创建一个此字符串对象,然后堆中再创建一个常量池中此”宜春”对象的拷贝对象。 也就是说准确答案是产生了一个或两个对象,如果常量池中原来没有 ”宜春” ,就是两个。...

技术大佬:我去,你写的 switch 语句也太老土了吧

昨天早上通过远程的方式 review 了两名新来同事的代码,大部分代码都写得很漂亮,严谨的同时注释也很到位,这令我非常满意。但当我看到他们当中有一个人写的 switch 语句时,还是忍不住破口大骂:“我擦,小王,你丫写的 switch 语句也太老土了吧!” 来看看小王写的代码吧,看完不要骂我装逼啊。 private static String createPlayer(PlayerTypes p...

和黑客斗争的 6 天!

互联网公司工作,很难避免不和黑客们打交道,我呆过的两家互联网公司,几乎每月每天每分钟都有黑客在公司网站上扫描。有的是寻找 Sql 注入的缺口,有的是寻找线上服务器可能存在的漏洞,大部分都...

讲一个程序员如何副业月赚三万的真实故事

loonggg读完需要3分钟速读仅需 1 分钟大家好,我是你们的校长。我之前讲过,这年头,只要肯动脑,肯行动,程序员凭借自己的技术,赚钱的方式还是有很多种的。仅仅靠在公司出卖自己的劳动时...

上班一个月,后悔当初着急入职的选择了

最近有个老铁,告诉我说,上班一个月,后悔当初着急入职现在公司了。他之前在美图做手机研发,今年美图那边今年也有一波组织优化调整,他是其中一个,在协商离职后,当时捉急找工作上班,因为有房贷供着,不能没有收入来源。所以匆忙选了一家公司,实际上是一个大型外包公司,主要派遣给其他手机厂商做外包项目。**当时承诺待遇还不错,所以就立马入职去上班了。但是后面入职后,发现薪酬待遇这块并不是HR所说那样,那个HR自...

女程序员,为什么比男程序员少???

昨天看到一档综艺节目,讨论了两个话题:(1)中国学生的数学成绩,平均下来看,会比国外好?为什么?(2)男生的数学成绩,平均下来看,会比女生好?为什么?同时,我又联想到了一个技术圈经常讨...

副业收入是我做程序媛的3倍,工作外的B面人生是怎样的?

提到“程序员”,多数人脑海里首先想到的大约是:为人木讷、薪水超高、工作枯燥…… 然而,当离开工作岗位,撕去层层标签,脱下“程序员”这身外套,有的人生动又有趣,马上展现出了完全不同的A/B面人生! 不论是简单的爱好,还是正经的副业,他们都干得同样出色。偶尔,还能和程序员的特质结合,产生奇妙的“化学反应”。 @Charlotte:平日素颜示人,周末美妆博主 大家都以为程序媛也个个不修边幅,但我们也许...

MySQL数据库面试题(2020最新版)

文章目录数据库基础知识为什么要使用数据库什么是SQL?什么是MySQL?数据库三大范式是什么mysql有关权限的表都有哪几个MySQL的binlog有有几种录入格式?分别有什么区别?数据类型mysql有哪些数据类型引擎MySQL存储引擎MyISAM与InnoDB区别MyISAM索引与InnoDB索引的区别?InnoDB引擎的4大特性存储引擎选择索引什么是索引?索引有哪些优缺点?索引使用场景(重点)...

如果你是老板,你会不会踢了这样的员工?

有个好朋友ZS,是技术总监,昨天问我:“有一个老下属,跟了我很多年,做事勤勤恳恳,主动性也很好。但随着公司的发展,他的进步速度,跟不上团队的步伐了,有点...

我入职阿里后,才知道原来简历这么写

私下里,有不少读者问我:“二哥,如何才能写出一份专业的技术简历呢?我总感觉自己写的简历太烂了,所以投了无数份,都石沉大海了。”说实话,我自己好多年没有写过简历了,但我认识的一个同行,他在阿里,给我说了一些他当年写简历的方法论,我感觉太牛逼了,实在是忍不住,就分享了出来,希望能够帮助到你。 01、简历的本质 作为简历的撰写者,你必须要搞清楚一点,简历的本质是什么,它就是为了来销售你的价值主张的。往深...

玩转springboot启动banner定义所得

最近接手了一个springboot项目,不是不熟悉这个框架,启动时打印的信息吸引了我。 这不是我熟悉的常用springboot的打印信息啊,我打开自己的项目: 还真是的,不用默认的感觉也挺高大上的。一时兴起,就去研究了一下源代码,还正是有些收获,稍后我会总结一下。正常情况下做为一个老程序员,是不会对这种小儿科感兴趣的,不就是一个控制台打印嘛。哈哈! 于是出于最初的好奇,研究了项目的源代码。看到

带了6个月的徒弟当了面试官,而身为高级工程师的我天天修Bug......

即将毕业的应届毕业生一枚,现在只拿到了两家offer,但最近听到一些消息,其中一个offer,我这个组据说客户很少,很有可能整组被裁掉。 想问大家: 如果我刚入职这个组就被裁了怎么办呢? 大家都是什么时候知道自己要被裁了的? 面试软技能指导: BQ/Project/Resume 试听内容: 除了刷题,还有哪些技能是拿到offer不可或缺的要素 如何提升面试软实力:简历, 行为面试,沟通能...

离职半年了,老东家又发 offer,回不回?

有小伙伴问松哥这个问题,他在上海某公司,在离职了几个月后,前公司的领导联系到他,希望他能够返聘回去,他很纠结要不要回去? 俗话说好马不吃回头草,但是这个小伙伴既然感到纠结了,我觉得至少说明了两个问题:1.曾经的公司还不错;2.现在的日子也不是很如意。否则应该就不会纠结了。 老实说,松哥之前也有过类似的经历,今天就来和小伙伴们聊聊回头草到底吃不吃。 首先一个基本观点,就是离职了也没必要和老东家弄的苦...

男生更看重女生的身材脸蛋,还是思想?

往往,我们看不进去大段大段的逻辑。深刻的哲理,往往短而精悍,一阵见血。问:产品经理挺漂亮的,有点心动,但不知道合不合得来。男生更看重女生的身材脸蛋,还是...

为什么程序员做外包会被瞧不起?

二哥,有个事想询问下您的意见,您觉得应届生值得去外包吗?公司虽然挺大的,中xx,但待遇感觉挺低,马上要报到,挺纠结的。

当HR压你价,说你只值7K,你该怎么回答?

当HR压你价,说你只值7K时,你可以流畅地回答,记住,是流畅,不能犹豫。 礼貌地说:“7K是吗?了解了。嗯~其实我对贵司的面试官印象很好。只不过,现在我的手头上已经有一份11K的offer。来面试,主要也是自己对贵司挺有兴趣的,所以过来看看……”(未完) 这段话主要是陪HR互诈的同时,从公司兴趣,公司职员印象上,都给予对方正面的肯定,既能提升HR的好感度,又能让谈判气氛融洽,为后面的发挥留足空间。...

面试:第十六章:Java中级开发(16k)

HashMap底层实现原理,红黑树,B+树,B树的结构原理 Spring的AOP和IOC是什么?它们常见的使用场景有哪些?Spring事务,事务的属性,传播行为,数据库隔离级别 Spring和SpringMVC,MyBatis以及SpringBoot的注解分别有哪些?SpringMVC的工作原理,SpringBoot框架的优点,MyBatis框架的优点 SpringCould组件有哪些,他们...

面试阿里p7,被按在地上摩擦,鬼知道我经历了什么?

面试阿里p7被问到的问题(当时我只知道第一个):@Conditional是做什么的?@Conditional多个条件是什么逻辑关系?条件判断在什么时候执...

终于懂了TCP和UDP协议区别

终于懂了TCP和UDP协议区别

你打算用Java 8一辈子都不打算升级到Java 14,真香

我们程序员应该抱着尝鲜、猎奇的心态,否则就容易固步自封,技术停滞不前。

无代码时代来临,程序员如何保住饭碗?

编程语言层出不穷,从最初的机器语言到如今2500种以上的高级语言,程序员们大呼“学到头秃”。程序员一边面临编程语言不断推陈出新,一边面临由于许多代码已存在,程序员编写新应用程序时存在重复“搬砖”的现象。 无代码/低代码编程应运而生。无代码/低代码是一种创建应用的方法,它可以让开发者使用最少的编码知识来快速开发应用程序。开发者通过图形界面中,可视化建模来组装和配置应用程序。这样一来,开发者直...

面试了一个 31 岁程序员,让我有所触动,30岁以上的程序员该何去何从?

最近面试了一个31岁8年经验的程序猿,让我有点感慨,大龄程序猿该何去何从。

大三实习生,字节跳动面经分享,已拿Offer

说实话,自己的算法,我一个不会,太难了吧

程序员垃圾简历长什么样?

已经连续五年参加大厂校招、社招的技术面试工作,简历看的不下于万份 这篇文章会用实例告诉你,什么是差的程序员简历! 疫情快要结束了,各个公司也都开始春招了,作为即将红遍大江南北的新晋UP主,那当然要为小伙伴们做点事(手动狗头)。 就在公众号里公开征简历,义务帮大家看,并一一点评。《启舰:春招在即,义务帮大家看看简历吧》 一石激起千层浪,三天收到两百多封简历。 花光了两个星期的所有空闲时...

《经典算法案例》01-08:如何使用质数设计扫雷(Minesweeper)游戏

我们都玩过Windows操作系统中的经典游戏扫雷(Minesweeper),如果把质数当作一颗雷,那么,表格中红色的数字哪些是雷(质数)?您能找出多少个呢?文中用列表的方式罗列了10000以内的自然数、质数(素数),6的倍数等,方便大家观察质数的分布规律及特性,以便对算法求解有指导意义。另外,判断质数是初学算法,理解算法重要性的一个非常好的案例。

《Oracle Java SE编程自学与面试指南》最佳学习路线图(2020最新版)

正确选择比瞎努力更重要!

Java岗开发3年,公司临时抽查算法,离职后这几题我记一辈子

前几天我们公司做了一件蠢事,非常非常愚蠢的事情。我原以为从学校出来之后,除了找工作有测试外,不会有任何与考试有关的事儿。 但是,天有不测风云,公司技术总监、人事总监两位大佬突然降临到我们事业线,叫上我老大,给我们组织了一场别开生面的“考试”。 那是一个风和日丽的下午,我翘着二郎腿,左手端着一杯卡布奇诺,右手抓着我的罗技鼠标,滚动着轮轴,穿梭在头条热点之间。 “淡黄的长裙~蓬松的头发...

立即提问
相关内容推荐