Palindrome Check

Given a string, return True if it reads the same forward and backward, and False otherwise. For example, "racecar" is a palindrome, "hello" is not. A single character like "a" is always a palindrome.

A palindrome is symmetric: the first character must equal the last, the second must equal the second-to-last, and so on. This is the exact same two-pointer technique used for array reversal — compare from both ends and move inward. If any pair mismatches, we can immediately return False.

1. Initialize two pointers: left = 0, right = len(s) - 1. 2. While left < right, compare s[left] with s[right]. 3. If they differ, return False immediately (not a palindrome). 4. If they match, move left forward and right backward. 5. If the loop completes without mismatches, return True.

- Comparing with s == s[::-1] — while correct, it uses O(N) extra space and doesn't demonstrate the two-pointer technique - Not handling case sensitivity: "Racecar" would return False unless you normalize to lowercase first - Forgetting edge cases: empty string "" and single character "a" are both palindromes

This problem reinforces the two-pointer pattern from Day 4 (Array Reversal). Strings in Python are essentially character arrays, so the same pointer logic applies. The early-exit optimization means we stop as soon as we find the first mismatch, making this efficient in practice.