leetcode-第10周双周赛-5099验证回文字符串③

题目描述：

方法：动态规划

class Solution:
    def isValidPalindrome(self, s: str, k: int) -> bool:
        def isKPalRec(str1, str2, m, n):
            dp = [[0] * (n + 1) for _ in range(m + 1)] 

            # Fill dp[][] in bottom up manner
            for i in range(m + 1): 

                for j in range(n + 1):
                    if not i :
                        dp[i][j] = j

                    elif not j :
                        dp[i][j] = i

                    elif (str1[i - 1] == str2[j - 1]):
                        dp[i][j] = dp[i - 1][j - 1] 

                    else:
                        dp[i][j] = 1 + min(dp[i - 1][j],  # Remove from str1
                                          (dp[i][j - 1])) # Remove from str2 

            return dp[m][n] 

        revStr = s[::-1]
        l = len(s) 

        return (isKPalRec(s, revStr, l, l) <= k * 2)

自底向上：

from functools import lru_cache
class Solution:
    def isValidPalindrome(self, s: str, k: int) -> bool:
        n = len(s)
        t = s[::-1]
        @lru_cache(None)
        def dp(i, j):
            if i == 0 or j == 0:
                return i + j
            i-=1;j-=1
            if s[i] == t[j]: return dp(i, j)
            return 1 + min(dp(i+1,j), dp(i,j+1))

        return dp(n, n) <= 2 * k