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If String is a Rotation of Another

Certification: Intermediate Level Accuracy: 0% Submissions: 0 Points: 10

Write a C# program to check if a given string is a palindrome without using any built-in string reversal functions like Reverse(), or any LINQ methods. A palindrome is a word, phrase, or sequence that reads the same backward as forward. For this problem, consider only alphanumeric characters and ignore case sensitivity.

Example 1
    
  
  • Input: str = "racecar"
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  • Output: true
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  • Explanation: 
    • Convert the string to lowercase: "racecar". 
    • Compare characters from both ends: 'r' == 'r' (positions 0 and 6). 
    • Move inward: 'a' == 'a' (positions 1 and 5). 
    • Continue: 'c' == 'c' (positions 2 and 4). 
    • Reach the middle character 'e' (position 3). 
    • All comparisons match, so "racecar" is a palindrome.
    •
Example 2
    
  
  • Input: str = "hello"
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  • Output: false
    • 
  
  • Explanation: 
    • Convert the string to lowercase: "hello". 
    • Compare characters from both ends: 'h' != 'o' (positions 0 and 4). 
    • Since the first comparison fails, "hello" is not a palindrome. 
    • No need to check further as we already found a mismatch.
    •
Constraints
    
  
  • 1 ≤ str.length ≤ 10^4
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  • str contains only alphanumeric characters and spaces
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  • You are not allowed to use built-in string reversal functions or LINQ
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  • Case should be ignored (treat 'A' and 'a' as the same)
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  • Time Complexity: O(n)
    • 
  
  • Space Complexity: O(1)
    •
StringsPhillipsOracle
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Hint
Solution

Solution Hints

    
  
  • Use two pointers approach - one starting from the beginning and one from the end
    • 
  
  • Convert characters to lowercase for case-insensitive comparison
    • 
  
  • Skip non-alphanumeric characters if present
    • 
  
  • Compare characters at both pointers and move them toward each other
    • 
  
  • If any comparison fails, return false immediately
    • 
  
  • If all comparisons pass, return true
    •

Steps to solve by this approach:

 Step 1: Create a clean version of the input string by removing spaces and non-alphanumeric characters, and convert all characters to lowercase.
 Step 2: Initialize two pointers - left starting at the beginning (index 0) and right starting at the end (last index) of the cleaned string.
 Step 3: Enter a while loop that continues as long as the left pointer is less than the right pointer.
 Step 4: Compare the characters at the left and right positions in the cleaned string.
 Step 5: If the characters don't match, immediately return false as the string is not a palindrome.
 Step 6: If the characters match, increment the left pointer and decrement the right pointer to move toward the center.
 Step 7: If the loop completes without finding any mismatches, return true as the string is a palindrome.

Submitted Code :