LeetCode - 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.

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