(Leet Code c++)FIrst Unique Character in a string

387. First Unique Character in a String

 

Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.

 

Example 1:

Input: s = "leetcode" Output: 0

Example 2:

Input: s = "loveleetcode" Output: 2

Example 3:

Input: s = "aabb" Output: -1

 

Constraints:

• 1 <= s.length <= 105
• s consists of only lowercase English letters.

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