C++

遍历unordered_map

leetcode 49字母异位词分组
class Solution {
public:
    vector> groupAnagrams(vector& strs) {
        unordered_map> map;
        for(auto str:strs)
        {
            string key = str;
            sort(key.begin(),key.end());
            map[key].push_back(str);
        }
        vector> res;
        for(auto iter=map.begin();iter!=map.end();iter++)
        {
            res.push_back(iter->second);
        }
        return res;
    }
};

字符串输入输出问题

intput 
3
11
antontrygub
15
bestcoordinator
19
trywatchinggurabruh
code 
#include
#include
#include

using namespace std;
const int N=210;
char s[N];
int main()
{
    int t=0;
    cin >> t;
    while(t--)
    {
        int n;
        cin >> n >> s;//输入string转为char[] 不需要s+n 直接输入s就行
        sort(s,s+n);
        for(int i=0;i

创建动态规划数组tle问题

创成bool数组不能过

class Solution {
public:
    string longestPalindrome(string s) {
        int n = s.size();
        vector<vector<bool>>f(n,vector<bool>(n,0));
        string res;
        for(int i=n-1;i>=0;i--)
        {
            for(int j=i;j<n;j++)
            {
                if(j-i+1>2)f[i][j]=s[i]==s[j]?f[i+1][j-1]:false;
                else f[i][j]=s[i]==s[j]?true:false;
                if(f[i][j]&&j-i+1>res.size())res = s.substr(i,j-i+1);        
            }
        }
        return res;
    }
};

创成int数组或者静态bool数组能过

const int N=100010;
bool f[n][n];

class Solution {
public:
    string longestPalindrome(string s) {
        int n = s.size();
        vector<vector<int>>f(n,vector<int>(n,0));
        string res;
        int l,r,maxi;
        for(int i=n-1;i>=0;i--)
        {
            for(int j=i;j<n;j++)
            {
                if(j-i+1>2&&s[i]==s[j])f[i][j]=f[i+1][j-1];
                else f[i][j]=s[i]==s[j]?1:0;
                if(f[i][j]==1&&j-i+1>maxi)
                {
                    l=i,r=j,maxi=j-i+1;
                }        
            }
        }
        return s.substr(l,r-l+1);
    }
};