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Palindrome Check

Certification: Basic Level Accuracy: 75% Submissions: 4 Points: 5

Write a JavaScript function to determine if a given string is a palindrome. A palindrome is a word, phrase, number, or other sequence of characters that reads the same forward and backward. For this problem, consider only alphanumeric characters and ignore case sensitivity.

Example 1
    
  
  • Input: s = "racecar"
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  • Output: true
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  • Explanation: 
    • The string "racecar" contains only lowercase letters. 
    • Reading from left to right: r-a-c-e-c-a-r. 
    • Reading from right to left: r-a-c-e-c-a-r. 
    • Both directions give the same sequence, so it's a palindrome.
    •
Example 2
    
  
  • Input: s = "A man, a plan, a canal: Panama"
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  • Output: true
    • 
  
  • Explanation: 
    • The string contains letters, spaces, and punctuation. 
    • Considering only alphanumeric characters: "AmanaplanacanalPanama". 
    • Converting to lowercase: "amanaplanacanalpanama". 
    • This reads the same forwards and backwards, so it's a palindrome.
    •
Constraints
    
  
  • 1 ≤ s.length ≤ 2 * 10^5
    • 
  
  • s consists only of printable ASCII characters
    • 
  
  • Consider only alphanumeric characters
    • 
  
  • Ignore case sensitivity
    • 
  
  • Time Complexity: O(n)
    • 
  
  • Space Complexity: O(1)
    •
StringsWalmartD. E. Shaw
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Hint
Solution

Solution Hints

    
  
  • Use two pointers approach: one from the beginning and one from the end
    • 
  
  • Skip non-alphanumeric characters when moving the pointers
    • 
  
  • Convert characters to lowercase for case-insensitive comparison
    • 
  
  • Move pointers toward each other and compare characters
    • 
  
  • If any pair doesn't match, return false
    • 
  
  • If all pairs match, return true
    •

Steps to solve by this approach:

 Step 1: Initialize two pointers, left at start and right at end of string
 Step 2: Create helper function to check if character is alphanumeric
 Step 3: Move left pointer forward, skipping non-alphanumeric characters
 Step 4: Move right pointer backward, skipping non-alphanumeric characters
 Step 5: Compare characters at both pointers after converting to lowercase
 Step 6: If characters don't match, return false immediately
 Step 7: Continue until pointers meet or cross, then return true

Submitted Code :