Longest Palindromic Subsequence (Leetcode 516)

Problem Link: https://leetcode.com/problems/longest-palindromic-subsequence/

class Solution:
    def longestPalindromeSubseq(self, s: str) -> int:
        
        n=len(s)
        s1=s
        s2=s[::-1]
        dp=[[0 for i in range(n+1)] for j in range(n+1)]
        for i in range(n+1):
            for j in range(n+1):
                if(i==0 or j==0):
                    dp[i][j]=0
                else:
                    if(s1[i-1]==s2[j-1]):
                        dp[i][j]=1+dp[i-1][j-1]
                    else:
                        dp[i][j]=max(dp[i-1][j],dp[i][j-1])
        return dp[n][n]