First Unique Character in a String LeetCode solution in C++

1
class Solution {
2
 public:
3
  int firstUniqChar(string s) {
4
    unordered_map<char, int> mp;
5

6
    for (int i = 0; i < s.length(); i++) {
7
      mp[s[i]]++;
8
    }
9

10
    for (int i = 0; i < s.length(); i++) {
11
      if (mp[s[i]] == 1) {
12
        return i;
13
      }
14
    }
15

16
    return -1;
17
  }
18
};