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    public int maxProduct(String[] words) {
        int n = words.length;
        int[] masks = new int[n];
        int[] lens = new int[n]; 
        for (int i = 0; i < n; i++) {
            lens[i] = words[i].length(); 
            for (char c : words[i].toCharArray()) {
                masks[i] |= 1 << (c - 'a');
            }
        }
        int max = 0;
        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n; j++) {
                if ((masks[i] & masks[j]) == 0) {
                    max = Math.max(max, lens[i] * lens[j]); 
                }
            }
        }
        return max;
    }