Valid Palindrome

Easy~15 min

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

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

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.

Example 3

Input: s = " "

Output: true

Explanation: After removing non-alphanumeric characters, s is an empty string. An empty string is a palindrome by definition.

Constraints

1 <= s.length <= 2 * 10^5
s consists only of printable ASCII characters
Expected time complexity: O(n)

Code

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Output

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