0387 - First Unique Character in a String

0387 - 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.

Examples

Input: s = "leetcode" Output: 0

Input: s = "loveleetcode" Output: 2

Input: s = "aabb" Output: -1

Constraints

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

Java Solution

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