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class Solution {

    public int maxProduct(String[] words) {

        Map<Integer, Integer> map = new HashMap<Integer, Integer>();

        int length = words.length;

        for (int i = 0; i < length; i++) {

            int mask = 0;

            String word = words[i];

            int wordLength = word.length();

            for (int j = 0; j < wordLength; j++) {

                mask |= 1 << (word.charAt(j) - 'a');

            }

            if (wordLength > map.getOrDefault(mask, 0)) {

                map.put(mask, wordLength);

            }

        }

        int maxProd = 0;

        Set<Integer> maskSet = map.keySet();

        for (int mask1 : maskSet) {

            int wordLength1 = map.get(mask1);

            for (int mask2 : maskSet) {

                if ((mask1 & mask2) == 0) {

                    int wordLength2 = map.get(mask2);

                    maxProd = Math.max(maxProd, wordLength1 * wordLength2);

                }

            }

        }

        return maxProd;

    }

}

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func maxProduct(words []string) int {

    hash := func(word string) int {

        res := 0

        for _, r := range word{

            res |= 1 << (r - 'a')

        }

        return res

    }

    m, ans := map[int]int{}, 0

    for _, word := range words {

        h := hash(word)

        if m[h] < len(word) {

            for other, v := range m {

                if((other & h) == 0){

                    if tmp := v * len(word); tmp > ans {

                        ans = tmp

                    }

                }

            }

            m[h] = len(word)

        }

    }

    return ans

}