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Grokking the Coding Interview Patterns in C++

Solution: Next Palindrome Using Same Digits

Explore how to compute the next smallest palindrome larger than an input numeric palindrome by rearranging its digits using the two pointers technique. Understand splitting the palindrome, finding the next lexicographical permutation of the left half, and mirroring it to form the resulting palindrome efficiently.

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Statement

Given a numeric string, numStr, representing a palindromeA palindrome is a number that reads the same backward as it does forward. (composed only of digits). Return the smallest palindrome larger than numStr that can be created by rearranging its digits. If no such palindrome exists, return an empty string "".

Consider the following example to understand the expected output for a given numeric string:

  • input string = "123321"

  • The valid palindromes made from the exact digits are "213312", "231132", "312213", "132231", "321123".

  • We return the palindrome "132231" because it is the smallest palindrome larger than the input string "123321".

Constraints:

  • ...