516. Longest Palindromic Subsequence

题目

Given a string s, find the longest palindromic subsequence's length in s. You may assume that the maximum length of s is 1000.

Example 1:

Input:
"bbbab"

Output:
4

One possible longest palindromic subsequence is "bbbb".

Example 2:

Input:
"cbbd"

Output:
2

One possible longest palindromic subsequence is "bb".

解题思路

见程序注释