Maximum Product of Word Lengths
描述
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.
分析
由于只有26个小写字母,所以,我们可以为数组中的每个word
开辟一个长为26的布尔数组作为哈希表,然后用一个两重for循环,两两比较,如果不存在公共的字母,则计算二者的长度的乘积,取最大作为最终结果。时间复杂度O(26n^2)
,空间复杂度O(26n)
。
上面的方法可以进一步优化,即长度为26的布尔数组,小于32位,可以编码为一个整数,这样两个整数按位与,如果结果为1,说明存在公共字母,如果结果为0,说明不存在公共字母。时间复杂度O(n^2)
,空间复杂度O(n)
。