Split two strings to make palindrome

Two Pointers String

32.1% acceptance

Feb 25, 2026

778

260

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

Solution

Rust

Time O(2^n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn check_palindrome_formation(a: String, b: String) -> bool {
    let a: Vec<u8> = a.bytes().collect();
    let b: Vec<u8> = b.bytes().collect();
    Self::check(&a, &b) || Self::check(&b, &a)
  }

  fn check(a: &[u8], b: &[u8]) -> bool {
    let n = a.len();
    let mut l = 0;
    let mut r = n - 1;
    while l < r && a[l] == b[r] {
      l += 1;
      r -= 1;
    }
    // middle part: check if a[l..=r] or b[l..=r] is palindrome
    Self::is_palindrome(a, l, r) || Self::is_palindrome(b, l, r)
  }

  fn is_palindrome(s: &[u8], mut l: usize, mut r: usize) -> bool {
    while l < r {
      if s[l] != s[r] { return false; }
      l += 1;
      r -= 1;
    }
    true
  }
}