Valid Palindrome — Easy Coding Interview Question

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. Given a string s, return true if it is a palindrome, or false otherwise.

Example

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

Output: true

Explanation: "amanaplanacanalpanama" is a palindrome.

Constraints

• 1 ≤ s.length ≤ 2 * 10⁵
• s consists only of printable ASCII characters

Topics & Companies

Topics: strings, two-pointers

Asked by: Amazon, Google, Meta, Microsoft, Apple, Bloomberg

Optimal Solution Complexity

Time complexity: O(n). Space complexity: O(1).

Practice more

• All DSA Problems
• DSA Patterns