What is the optimal time complexity of solving Valid Palindrome?

The optimized solution achieves a time complexity of O(n) by using sorting, mathematical shortcuts, or hash table lookups.

What is the auxiliary space complexity for Valid Palindrome?

The space complexity is O(n) since we only use a minimal/constant amount of extra memory for tracking variables (or auxiliary space if dynamic structures are allocated).

What are the typical edge cases we must handle in Valid Palindrome?

Key edge cases include empty collections, negative or large bounds causing integer overflow, arrays with only one element, or inputs where target criteria are not met.

How can we optimize the brute force approach for Valid Palindrome?

Brute force methods often inspect all possible combinations. We optimize this by sorting the input list to enable binary search, or tracking processed items in a set to avoid redundant nested loop lookups.

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Valid Palindrome

Learn how to solve the 'Valid Palindrome' problem. This detailed resource details brute force and optimized approaches.

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Problem Statement

Easy

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. Alphanumeric characters include letters and numbers.

Given a string s, return True if it is a palindrome, or False otherwise.

Write a function isPalindrome(s: str) -> bool.

Constraints

•1 <= len(s) <= 2 * 10^5
•s consists only of printable ASCII characters

Examples

Example 1

Input

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

Output

True

Explanation

After removing non-alphanumeric characters and converting to lowercase: "amanaplanacanalpanama", which is a palindrome.

Example 2

Input

s = "race a car"

Output

False

Explanation

After processing: "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.

Need a Hint?

Use two pointer variables starting at different bounds (e.g. left = 0, right = length - 1) and shrink the search window.

Edge Cases to Watch

Empty list or null input variables
Single item lists/arrays
Extremely large input bounds causing integer or stack overflow

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