Valid Palindrome Solution for Cognizant

Company: Cognizant · Difficulty: Easy · Topics: String, Two Pointers

Problem Statement

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward.

Examples

Example 1:

Input: s = "A man, a plan, a canal: Panama"

Output: true

Explanation: "amanaplanacanalpanama" is a palindrome.

Example 2:

Input: s = "race a car"

Output: false

Explanation: "raceacar" is not a palindrome.

Approach

Use two pointers (left and right) to compare characters from both ends, skipping non-alphanumeric characters.

Time and Space Complexity

• Time Complexity: O(n)
• Space Complexity: O(1)

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