README.md

1771. Maximize Palindrome Length From Subsequences

You are given two strings, word1 and word2. You want to construct a string in the following manner:

• Choose some non-empty subsequence subsequence1 from word1.
• Choose some non-empty subsequence subsequence2 from word2.
• Concatenate the subsequences: subsequence1 + subsequence2, to make the string.

Return the length of the longest palindrome that can be constructed in the described manner. If no palindromes can be constructed, return 0.

A subsequence of a string s is a string that can be made by deleting some (possibly none) characters from s without changing the order of the remaining characters.

A palindrome is a string that reads the same forward as well as backward.

Example 1:

Input: word1 = "cacb", word2 = "cbba" Output: 5 Explanation: Choose "ab" from word1 and "cba" from word2 to make "abcba", which is a palindrome. 

Example 2:

Input: word1 = "ab", word2 = "ab" Output: 3 Explanation: Choose "ab" from word1 and "a" from word2 to make "aba", which is a palindrome. 

Example 3:

Input: word1 = "aa", word2 = "bb" Output: 0 Explanation: You cannot construct a palindrome from the described method, so return 0. 

Constraints:

• 1 <= word1.length, word2.length <= 1000
• word1 and word2 consist of lowercase English letters.

Solutions (Python)

1. Solution

fromfunctoolsimportcacheclassSolution: deflongestPalindrome(self, word1: str, word2: str) ->int: @cachedeflongestSubPalindrome(i: int, j: int) ->int: ifi>j: return0ifi==j: return1ret=max(longestSubPalindrome(i, j-1), longestSubPalindrome(i+1, j)) ifword[i] ==word[j]: ret=max(ret, 2+longestSubPalindrome(i+1, j-1)) returnretword=word1+word2first= [[-1, -1] for_inrange(26)] ret=0foriinrange(len(word1) -1, -1, -1): first[ord(word1[i]) -97][0] =iforiinrange(len(word1), len(word)): first[ord(word[i]) -97][1] =ifori, jinfirst: ifi>=0andj>=0: ret=max(ret, 2+longestSubPalindrome(i+1, j-1)) returnret