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.

Solution

 public int firstUniqChar(String s) {
        HashMap<Character, Integer> count = new HashMap<>();
        int len = s.length();
        for(int i = 0; i < len; i++){
            count.put(s.charAt(i), count.getOrDefault(s.charAt(i), 0) + 1);
        }
        for(int i = 0; i < len; i++){
            if(count.get(s.charAt(i)) == 1){
                return i;
            }
        }
        return -1;
    }