class Solution {
public:
vector<int> shuffle(vector<int>& nums, int n) {
vector<int> res;
for(int i=0;i<n;i++){
res.push_back(nums[i]);
res.push_back(nums[n+i]);
}
return res;
}
};
前缀和思想
class Solution {
public:
vector<int> runningSum(vector<int>& nums) {
int n = nums.size();
for (int i = 1; i < n; i++) {
nums[i] += nums[i - 1];
}
return nums;
}
};
class Solution {
public:
string reverseLeftWords(string s, int n) {
s += s.substr(0,n);
return s.substr(n,s.length()-n);
}
};
class Solution {
public:
string replaceSpace(string s) {
for(int i=0;i<s.size();i++){
if(s[i]==' '){
s.erase(s.begin()+i);
s.insert(i,"%20");
}
}
return s;
}
};
class Solution {
public:
string replaceSpace(string s) {
string s1;
for(int i=0;i<s.size();i++)
{
if(s[i]==' ') s1+="%20";
else s1+=s[i];
}
return s1;
}
};
class Solution {
public:
string replaceSpace(string s) {
for(int i=0;i<s.size();i++)
{
if(s[i]==' ') s=s.replace(i,1,"%20");
}
return s;
}
};
stl摸鱼系列
哈希
class Solution {
public:
vector<int> smallerNumbersThanCurrent(vector<int>& nums) {
vector<int> v=nums;
sort(v.begin(),v.end());
int hash[110];
for(int i=v.size()-1;i>=0;i--)
hash[v[i]]=i;
for(int i=0;i<nums.size();i++)
v[i]=hash[nums[i]];
return v;
}
};
class Solution {
public:
vector<int> printNumbers(int n) {
vector<int> ans(pow(10,n)-1);
iota(begin(ans),end(ans),1);
return ans;
}
};
class Solution {
public:
vector<int> printNumbers(int n) {
vector<int> ans;
// 最大的n位数
int t = pow(10, n) - 1;
for(int i = 1; i <= t; i++){
ans.push_back(i);
}
return ans;
}
};
那么问题来了,为什么y1不能设为全局变量?