Question

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode" return 0. s = "loveleetcode", return 2.

Note: You may assume the string contain only lowercase letters.

Solution

class Solution {
public:
    int firstUniqChar(string s) {
      std::vector<int> string_set(128);
      for(int i = 0; i < s.size(); ++i) string_set[s[i]]++;
      for(int i = 0; i < s.size(); ++i) {
        if(string_set[s[i]] == 1) return i;
      }
      return -1;
    }
};