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

「 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: a_prefix and a_suffix where a = a_prefix + a_suffix, and splitting b into two strings: b_prefix and b_suffix where b = b_prefix + b_suffix. Check if a_prefix + b_suffix or b_prefix + a_suffix forms a palindrome.

When you split a string s into s_prefix and s_suffix, either s_suffix or s_prefix 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:
• a_prefix = "", a_suffix = "x"
• b_prefix = "", b_suffix = "y"
• Then, a_prefix + b_suffix = "" + "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:

• a_prefix = "ula", a_suffix = "cfd"

• b_prefix = "jiz", b_suffix = "alu"

• Then, a_prefix + b_suffix = "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
 Copy code 

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 ：a_prefix and a_suffix, among a = a_prefix + a_suffix, take b Split into two strings ：b_prefix and b_suffix, among b = b_prefix + b_suffix. Check a_prefix + b_suffix or b_prefix + a_suffix Whether palindromes are formed .

The string s Split into s_prefix and s_suffix when , allow s_suffix or s_prefix 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
        

        	      
		
 Copy code 

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.
 Copy code 

Original link ：leetcode.com/problems/sp…

Your support is my greatest motivation