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leetcode 1616. Split Two Strings to Make Palindrome (python)

2022-02-01 12:02:26 Wang Daya

「 This is my participation 11 The fourth of the yuegengwen challenge 27 God , Check out the activity details :2021 One last more challenge

describe

You are given two strings a and b of the same length. Choose an index and split both strings at the same index, splitting a into two strings: aprefix and asuffix where a = aprefix + asuffix, and splitting b into two strings: bprefix and bsuffix where b = bprefix + bsuffix. Check if aprefix + bsuffix or bprefix + asuffix forms a palindrome.

When you split a string s into sprefix and ssuffix, either ssuffix or sprefix is allowed to be empty. For example, if s = "abc", then "" + "abc", "a" + "bc", "ab" + "c" , and "abc" + "" are valid splits.

Return true if it is possible to form a palindrome string, otherwise return false.

Notice that x + y denotes the concatenation of strings x and y.

Example 1:

  • Input: a = "x", b = "y"
  • Output: true
  • Explaination: If either a or b are palindromes the answer is true since you can split in the following way:
  • aprefix = "", asuffix = "x"
  • bprefix = "", bsuffix = "y"
  • Then, aprefix + bsuffix = "" + "y" = "y", which is a palindrome.

Example 2:

  • Input: a = "abdef", b = "fecab"
  • Output: true

Example 3:

  • Input: a = "ulacfd", b = "jizalu"

  • Output: true

  • Explaination: Split them at index 3:

  • aprefix = "ula", asuffix = "cfd"

  • bprefix = "jiz", bsuffix = "alu"

  • Then, aprefix + bsuffix = "ula" + "alu" = "ulaalu", which is a palindrome.

Example 4:

  • Input: a = "xbdef", b = "xecab"
  • Output: false

Note:

1 <= a.length, b.length <= 10^5
a.length == b.length
a and b consist of lowercase English letters
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analysis

According to the meaning , Give two strings of the same length a and b. Select an index and split two strings at the same index , take a Split into two strings :aprefix and asuffix, among a = aprefix + asuffix, take b Split into two strings :bprefix and bsuffix, among b = bprefix + bsuffix. Check aprefix + bsuffix or bprefix + asuffix Whether palindromes are formed .

The string s Split into sprefix and ssuffix when , allow ssuffix or sprefix It's empty . for example , If s = "abc", be "" + "abc"、"a" + "bc"、"ab" + "c" and "abc" + "" Is a valid split . If a palindrome string can be formed, it returns True , Otherwise return to False. Please note that ,x + y Representation string x and y Series connection of .

In fact, it's easy to use greedy thinking in this problem , Join us and we have two strings a and b , And the position divided by the midline assumption , as follows :

  • a:AB | CD | EF
  • b:GH | KJ | LM

If a And b The suffix of can form palindromes , that AB Definitely and LM Can form palindromes , Then just judge and CD perhaps KJ Whether it is a palindrome , namely :AB+CD+LM perhaps AB+KJ+LM These two situations can form palindromes . take b And a The suffixes of form palindromes are the same logic .

answer

class Solution(object):
    def checkPalindromeFormation(self, a, b):
        """
        :type a: str
        :type b: str
        :rtype: bool
        """
        return self.check(a, b) or self.check(b,a)
    
    def check(self, a, b):
        if len(a) == 1 : return True
        i = 0
        j = len(a) - 1
        while i<=j and a[i]==b[j]:
            i+=1
            j-=1
        if i>j:return True
        return self.isPalindrome(a[i:j+1]) or self.isPalindrome(b[i:j+1])
    
    def isPalindrome(self, s):
        i = 0
        j = len(s)-1
        while i<=j and s[i]==s[j]:
            i+=1
            j-=1
        return i>j
        

        	      
		
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Running results

Runtime: 119 ms, faster than 66.67% of Python online submissions for Split Two Strings to Make Palindrome.
Memory Usage: 15.6 MB, less than 38.10% of Python online submissions for Split Two Strings to Make Palindrome.
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Original link :leetcode.com/problems/sp…

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