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Longest Palindrome in a String
Medium Accuracy: 49.2% Submissions: 66191 Points: 4

Given a string S, find the longest palindromic substring in S. Substring of string S: S[ i . . . . j ] where 0 ≤ i ≤ j < len(S). Palindrome string: A string which reads the same backwards. More formally, S is palindrome if reverse(S) = S. Incase of conflict, return the substring which occurs first ( with the least starting index).

Example 1:

Input:
S = "aaaabbaa"
Output: aabbaa
Explanation: The longest Palindromic
substring is "aabbaa".

Example 2:

Input:
S = "abc"
Output: a
Explanation: "a", "b" and "c" are the
longest palindromes with same length.
The result is the one with the least
starting index.

You don't need to read input or print anything. Your task is to complete the function longestPalin() which takes the string S as input and returns the longest palindromic substring of S.

Expected Time Complexity: O(|S|2).
Expected Auxiliary Space: O(1).

Constraints:
1 ≤ |S| ≤ 103