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Quick Sort

Certification: Advanced Level Accuracy: 0% Submissions: 0 Points: 15

Write a C++ program that implements the quick sort algorithm. The program should take an unsorted array of integers and sort it in ascending order using the divide-and-conquer strategy with a pivot element.

Example 1
    

  • Input: array = [10, 7, 8, 9, 1, 5]
    • 

  • Output: [1, 5, 7, 8, 9, 10]
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  • Explanation: 
  
      
    
    • Step 1: Choose last element as pivot (5)
      • 
    
    • Step 2: Partition array - elements smaller than pivot go left, larger go right
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    • Step 3: After first partition: [1, 5, 8, 9, 10, 7]
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    • Step 4: Recursively apply to subarrays [1] and [8, 9, 10, 7]
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    • Step 5: Continue until all subarrays are sorted
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    • Step 6: Return sorted array [1, 5, 7, 8, 9, 10]
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    •
Example 2
    

  • Input: array = [9, 8, 7, 6, 5, 4, 3, 2, 1]
    • 

  • Output: [1, 2, 3, 4, 5, 6, 7, 8, 9]
    • 

  • Explanation: 
  
      
    
    • Step 1: Choose last element as pivot (1)
      • 
    
    • Step 2: Partition array - all elements are larger than pivot
      • 
    
    • Step 3: After first partition: [1, 9, 8, 7, 6, 5, 4, 3, 2]
      • 
    
    • Step 4: Recursively apply to subarray [9, 8, 7, 6, 5, 4, 3, 2]
      • 
    
    • Step 5: Continue until all subarrays are sorted
      • 
    
    • Step 6: Return sorted array [1, 2, 3, 4, 5, 6, 7, 8, 9]
      • 
  
    

    •
Constraints
    

  • 1 ≤ array.length ≤ 10^5
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  • -10^6 ≤ array[i] ≤ 10^6
    • 

  • Time Complexity: O(n log n) average case, O(n²) worst case, where n is the length of the array
    • 

  • Space Complexity: O(log n) for the recursive call stack
    •
ArraysControl StructuresAlgorithmsDeloitteZomato
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Hint
Solution

Solution Hints

    
  
  • Choose a pivot element from the array (typically the last element).
    • 
  
  • Partition the array around the pivot: elements less than the pivot go to the left, elements greater go to the right.
    • 
  
  • Recursively apply the above steps to the sub-arrays.
    • 
  
  • Create a helper function to handle the partitioning process.
    • 
  
  • The base case of the recursion is when the subarray size becomes 1 or 0, which is already sorted.
    •

Steps to solve by this approach:

 Step 1: Implement a partition function that chooses a pivot element.

 Step 2: Rearrange the array so elements smaller than pivot are on left.

 Step 3: Move elements greater than pivot to the right of pivot.

 Step 4: Return the pivot's final position after partitioning.

 Step 5: Apply recursive quicksort to the left partition.

 Step 6: Apply recursive quicksort to the right partition.

 Step 7: Base case: arrays with 0 or 1 elements are already sorted.

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