Longest Palindromic Subsequence

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".

这是一道典型的dp题，用dp[][]来存储i,j两个pointer指向的string的一个char, 分别按照相等和不相等来处理即可。

 class Solution {
     public int longestPalindromeSubseq(String s) {
         int length = s.length();
         int[][] dp = new int[length][length];
         for (int i = ; i < length; i++) {
             dp[i][i] = ;
         }
         for (int subLength = ; subLength <= length; subLength++) {
             for (int i = ; i + subLength <= length; i++) {
                 int j = subLength + i - ;
                 if (s.charAt(i) == s.charAt(j)) {
                     dp[i][j] = dp[i + ][j - ] + ;
                 } else {
                     dp[i][j] = Math.max(dp[i + ][j], dp[i][j - ]);
                 }
             }
         }
         return dp[][length - ];
     }
 }