387. First Unique Character in a String

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.

 

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