Leetcode 389 Find the Difference

Leetcode 389 Find the Difference

#include <vector>#include <string>using namespace std;class Solution {public:    char findTheDifference(string s, string t) {      vector<int> lettercount(26,0);      for(int i = 0;i < s.length();i ++)      {          lettercount[s[i] - 'a'] ++;      }      for(int i = 0; i < t.length();i ++)      {          lettercount[t[i] - 'a'] --;          if(lettercount[t[i] - 'a'] < 0)          return t[i];      }    }     char findTheDifference1(string s, string t) {      char c = 0;      for(int i = 0;i < s.length();i ++)      {          c ^= s[i];      }      for(int i = 0; i < t.length();i ++)      {          c ^= t[i];      }      return c;    }    char findTheDifference2(string s, string t) //to learn    {        char c = 0;        for (auto ch : s) c ^= ch;        for (auto ch : t) c ^= ch;        return c;    }};