Java use HashMap solution

  • 0

    Use HashMap to record index of each char. If the char is duplicated, change the index to MAX_VALUE. Then get the lowest index from map.

    public int firstUniqChar(String s) {
        int res = Integer.MAX_VALUE;
        Map<Character, Integer> map = new HashMap<Character, Integer>();
        for (int i = 0; i < s.length(); i++){
            char c = s.charAt(i);
            if (map.containsKey(c)){
                map.put(c, Integer.MAX_VALUE);
                map.put(c, i);
        for (char c : map.keySet()){
            res = Math.min(res, map.get(c));
        if (res == Integer.MAX_VALUE)//corner case: if there is no unique char
            return -1;
        return res;

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