记一次=引起的血案

如果从时间上看, 是用了两个小时的时间在这个问题上面.

那么最后是什么原因呢

有错误的python代码

class Solution(object):
    def longestPalindrome(self, s):
        """
        :type s: str
        :rtype: str
        """
        n = len(s)
        if n==0:
          return s
        elif n ==1:
          return s
        
        dp = [[False]*n for _ in range(n)]
        
        # 表示未知解答
        max_idx = -1
        max_len = -1
        
        for i in range(n):
          dp[i][i] = True
          max_idx = i
          max_len = 1
        
        for i in range(1,n):
          if (s[i] == s[i-1]):
            dp[i-1][i] == True
            max_idx = i-1
            max_len = 2
        

        for strlen in range(3,n+1):
          # 注意下标
          for i in range(0,n-strlen+1):
            j = i+strlen-1
            
            if s[i] == s[j] and dp[i+1][j-1] == True:
              dp[i][j] = True
              if(strlen>max_len):
                max_idx = i
                max_len =strlen
        
        return s[max_idx:max_idx+max_len]

正确的python代码

class Solution(object):
    def longestPalindrome(self, s):
        """
        :type s: str
        :rtype: str
        """
        n = len(s)
        if n==0:
          return s
        elif n ==1:
          return s
        
        dp = [[False]*n for _ in range(n)]
        
        # 表示未知解答
        max_idx = -1
        max_len = -1
        
        for i in range(n):
          dp[i][i] = True
          max_idx = i
          max_len = 1
        
        for i in range(1,n):
          if (s[i] == s[i-1]):
            dp[i-1][i] == True
            max_idx = i-1
            max_len = 2
        

        for strlen in range(3,n+1):
          # 注意下标
          for i in range(0,n-strlen+1):
            j = i+strlen-1
            
            if s[i] == s[j] and dp[i+1][j-1] == True:
              dp[i][j] = True
              if(strlen>max_len):
                max_idx = i
                max_len =strlen
        
        return s[max_idx:max_idx+max_len]

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