EasyTwo Pointers

Is Palindrome II

Check palindrome with alphanumeric only

Solution Approach

Two pointers from both ends. Skip non-alphanumeric characters and compare in lowercase.

Implementation

def isPalindrome(s):
    left, right = 0, len(s) - 1
    while left < right:
        while left < right and not s[left].isalnum():
            left += 1
        while left < right and not s[right].isalnum():
            right -= 1
        if s[left].lower() != s[right].lower():
            return False
        left += 1
        right -= 1
    return True

Complexity Analysis

Time Complexity

O(n)

Space Complexity

O(1)

Complexity

Time:O(n)

Space:O(1)

Asked at

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