FirstUniqueCharacterInString

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.

s=""
return -1;

Note:

You may assume the string contain only lowercase letters.

public class Solution{
    public int firstUniqChar(String s){
        if (s == null || s.equals("")) return -1;
        char[] c = s.toCharArray();
        int[] cnt = new int[256];
                
        for (int i = 0; i < c.length; i++) {
            cnt[c[i]]++;
            System.out.println(cnt[c[i]]);
        }

        for (int i = 0; i < c.length; i++) {
            if (cnt[c[i]] == 1) return i; 
        }
        return -1;
    }
}