387. First Unique Character in a String

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

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