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.
这个题主要是怎么辨别两个字符串有相同的字母，使用一个32位的int，使用其中的26位来记录一个词中出现了哪些字母，那么只要把这个int相与就知道两个字符串是不是有重复字母了，没有重复字母的话这个结果应该是0，接下来计算乘积就好了。
var maxProduct = function(words) {
var words_array = [];
words.forEach(function(word){
var len = word.length;
var tmp_num = 0;
for(var i=0;i<len;i++){
tmp_num |= (1<<(word.charCodeAt(i)-48));
}
words_array.push(tmp_num);
});
var words_len = words_array.length;
var ret = 0;
var tmp = 0;
words_array.forEach(function(word,s){
for(var j=s+1;j<words_len;j++){
if((words_array[j] & words_array[s])===0){
tmp = words[j].length*words[s].length;
if(tmp>ret){
ret = tmp;
}
}
}
});
return ret;
};
