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Valid Palindrome II

Certification: Basic Level Accuracy: 0% Submissions: 0 Points: 8

Write a JavaScript program to determine if a string can be a palindrome after removing at most one character from it. A palindrome reads the same forwards and backwards.

Example 1
    
  
  • Input: s = "aba"
    • 
  
  • Output: true
    • 
  
  • Explanation: 
    • The string "aba" is already a palindrome. 
    • No character removal is needed. 
    • Therefore, it's valid with at most one character removal.
    •
Example 2
    
  
  • Input: s = "abca"
    • 
  
  • Output: true
    • 
  
  • Explanation: 
    • The string "abca" is not a palindrome initially. 
    • If we remove character 'c' at index 2, we get "aba". 
    • The string "aba" is a palindrome. 
    • Therefore, removing one character makes it a valid palindrome.
    •
Constraints
    
  
  • 1 ≤ s.length ≤ 10^5
    • 
  
  • s consists only of lowercase English letters
    • 
  
  • At most one character can be removed
    • 
  
  • Time Complexity: O(n)
    • 
  
  • Space Complexity: O(1)
    •
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Hint
Solution

Solution Hints

    
  
  • Use two pointers approach starting from both ends of the string
    • 
  
  • If characters at both pointers match, move both pointers inward
    • 
  
  • If characters don't match, try removing either the left or right character
    • 
  
  • Check if the remaining substring is a palindrome after removal
    • 
  
  • Create a helper function to check if a substring is a palindrome
    • 
  
  • Return true if removing one character results in a palindrome, false otherwise
    •

Steps to solve by this approach:

 Step 1: Initialize two pointers, left at the beginning and right at the end of the string.
 Step 2: Compare characters at left and right pointers while moving them toward each other.
 Step 3: If characters match, increment left pointer and decrement right pointer.
 Step 4: If characters don't match, we have found a mismatch point.
 Step 5: Try two possibilities: remove the left character or remove the right character.
 Step 6: Check if either of the remaining substrings forms a palindrome using helper function.
 Step 7: Return true if the string is already a palindrome or if removing one character makes it palindrome.

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