LeetCode 389. Find the Difference

Given two strings s and t which consist of only lowercase letters.

String t is generated by random shuffling string s and then add one more letter at a random position.

Find the letter that was added in t.

Example:

Input:
s = "abcd"
t = "abcde"

Output:
e

Explanation:
'e' is the letter that was added.

class Solution {
public:
    char findTheDifference(string s, string t) {
        map<char,int> count;
        for(int i=0;i<s.size();i++)
            count[s[i]]++;
        for(int i=0;i<t.size();i++){
            count[t[i]]--;
            if(count[t[i]]==-1)
               return t[i];
        }
    }
};