387.First_Unique_Character_in_a_String.cpp

class Solution {
public:
    int firstUniqChar(string s) {
        int count[26] = {0};
        for (int i = 0; i < s.length(); i++) {
            count[s[i]-'a']++;
        }
        for (int i = 0; i < s.length(); i++) {
            if (count[s[i]-'a'] == 1) {
                return i;
            }
        }
        return -1;
    }
};