Description:

This PR adds a solution to LeetCode Problem 1312 using a top-down dynamic programming approach with memoization.The goal is to return the minimum number of insertions required to make the input string a palindrome.

Approach:
We use recursion with memoization (top-down DP) to avoid redundant computations.

The key idea:

If characters at both ends match, move inward.

Else, insert one character and recursively solve for both possible substrings (excluding one character from either end), and take the minimum.