Given a string array words, find the maximum value of length(word[i]) * length(word[j]) where the two words do not share common letters. You may assume that each word will contain only lower case letters. If no such two words exist, return 0.

Example 1:

Given ["abcw", "baz", "foo", "bar", "xtfn", "abcdef"]

Return 16

The two words can be "abcw", "xtfn".

Example 2:

Given ["a", "ab", "abc", "d", "cd", "bcd", "abcd"]

Return 4

The two words can be "ab", "cd".

Example 3:

Given ["a", "aa", "aaa", "aaaa"]

Return 0

No such pair of words.

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1 public class Solution { 2     public int maxProduct(String[] words) { 3         int ans = 0; 4         int[] bitmap = new int[words.length]; 5          6         for(int i = 0; i < words.length; i++){ 7             for(int j = 0; j < words[i].length(); j++){ 8                 bitmap[i] |= 1 << (words[i].charAt(j) - 'a'); 9             }10         }11         12         for(int i = 0; i < bitmap.length; i++){13             for(int j = i+1; j < bitmap.length; j++){14                 if((bitmap[i] & bitmap[j]) == 0 && words[i].length()*words[j].length() > ans){15                     ans = words[i].length()*words[j].length();16                 }17             }18         }19         20         return ans;21     }22 }

之前都没有做过类似的题目，题目要找出字符串数组中两个 没有一个字母相同的字符串乘积的最大值，学习了大神的做法。

字母只有26个，java 中一个int 有32位。

通过 bitmap[i] |= 1 << (words[i].charAt(j) - 'a'); 即可记录下下标为i的字符串字符特征。 全部扫描一遍，即可记录所有的字符串特征， 之后二重循环即可得答案。