516 Longest Palindromic Subsequence¶
Problem¶
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:
Output: One possible longest palindromic subsequence is "bbbb". Example 2: Input: Output: One possible longest palindromic subsequence is "bb".Solutions¶
class Solution {
public int longestPalindromeSubseq(String s) {
int[][] dp = new int[s.length()][s.length()];
for (int l = 1; l <= s.length(); l ++) {
for (int i = 0; i + l - 1 < s.length(); i ++) {
int j = i + l - 1;
if (l == 1) {
dp[i][j] = 1;
continue;
}
if (l == 2) {
dp[i][j] = s.charAt(i) == s.charAt(j)?2:1;
continue;
}
dp[i][j] = Math.max(dp[i][j - 1], dp[i + 1][j]);
if (s.charAt(i) == s.charAt(j)) {
dp[i][j] = Math.max(dp[i][j], dp[i + 1][j - 1] + 2);
}
}
}
return dp[0][s.length() - 1];
}
}