python-leetcode-最长回文子序列

516. 最长回文子序列 - 力扣（LeetCode）

class Solution:
    def longestPalindromeSubseq(self, s: str) -> int:
        n = len(s)
        dp = [[0] * n for _ in range(n)]
        
        # 初始化：单个字符的最长回文子序列长度为 1
        for i in range(n):
            dp[i][i] = 1
        
        # 逐步填充 dp 表，从下往上，从左到右
        for length in range(2, n+1):  # 子串长度
            for i in range(n - length + 1):
                j = i + length - 1  # 计算区间 [i, j]
                if s[i] == s[j]:
                    dp[i][j] = dp[i+1][j-1] + 2
                else:
                    dp[i][j] = max(dp[i+1][j], dp[i][j-1])
        
        return dp[0][n-1]