public int longestSubStr(String str) {
        int max = 0;
        Deque<Character> deque = new ArrayDeque<>();

        for (int i = 0; i < str.length(); i++) {
            if (!deque.contains(str.charAt(i))) {
                deque.addLast(str.charAt(i));
            } else {
                max = Math.max(max, deque.size());
                while (deque.peek() != str.charAt(i)) {
                    deque.removeFirst();
                }
                deque.removeFirst();
                deque.addLast(str.charAt(i));
            } 
        }
        max = Math.max(max, deque.size());

        return max;
    }