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Reverse a String

Certification: Basic Level Accuracy: 75.61% Submissions: 41 Points: 5

Write a Java program to implement the reverseString(char[] s) function, which reverses a string in-place.

Example 1
    

  • Input: s = ['h', 'e', 'l', 'l', 'o']
    • 

  • Output: ['o', 'l', 'l', 'e', 'h']
    • 

  • Explanation:

      

    • Swap 'h' and 'o'
      • 

    • Swap 'e' and 'l'
      • 

    • 'l' stays → final array is reversed
      • 

    

    •
Example 2
    

  • Input: s = ['H', 'a', 'n', 'n', 'a', 'h']
    • 

  • Output: ['h', 'a', 'n', 'n', 'a', 'H']
    • 

  • Explanation:

      

    • Swap pairs until midpoint
      • 

    • Characters reversed in-place
      • 

    

    •
Constraints
    

  • 1 ≤ s.length ≤ 10^5
    • 

  • s[i] is a printable ascii character
    • 

  • Time Complexity: O(n)
    • 

  • Space Complexity: O(1)
    •
StringsD. E. ShawOracle
Editorial

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Hint
Solution

Solution Hints

    
  
  • Use two pointers, one at the start and one at the end of the array
    • 
  
  • Swap the characters at the two pointers
    • 
  
  • Move the left pointer to the right and the right pointer to the left
    • 
  
  • Continue until the pointers meet in the middle
    •

Steps to solve by this approach:

 Step 1: Initialize two pointers, left at the start of the array (index 0) and right at the end (index length-1).
 Step 2: While the left pointer is less than the right pointer, perform steps 3-5.
 Step 3: Swap the characters at the left and right pointers.
 Step 4: Increment the left pointer.
 Step 5: Decrement the right pointer.
 Step 6: Continue until the pointers meet in the middle or cross each other.

Submitted Code :