516 Longest Palindromic Subsequence

class Solution(object):
    def longestPalindromeSubseq(self, s):
        """
        :type s: str
        :rtype: int
        """
        n = len(s)
        dp = [[0 for i in range(n)] for j in range(n)]

        for i in range(n-1, -1, -1):
            dp[i][i] = 1
            for j in range(i+1, n, 1):
                if s[i] == s[j]:
                    dp[i][j] = dp[i+1][j-1] + 2
                else:
                    dp[i][j] = max(dp[i][j-1], dp[i+1][j])

        return dp[0][n-1]