C#: Quick sort

Last update on December 20 2024 12:52:45 (UTC/GMT +8 hours)

Write a C# Sharp program to sort a list of elements using Quick sort.

Quick sort is a comparison sort, meaning that it can sort items of any type for which a "less-than" relation (formally, a total order) is defined.

Pictorial presentation - Quick Sort algorithm :

Animation credits : RolandH

Sample Solution:-

C# Sharp Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Quick_Sort
{
    class Program
    {
        // Method to perform Quick Sort on an array
        private static void Quick_Sort(int[] arr, int left, int right) 
        {
            // Check if there are elements to sort
            if (left < right)
            {
                // Find the pivot index
                int pivot = Partition(arr, left, right);

                // Recursively sort elements on the left and right of the pivot
                if (pivot > 1) {
                    Quick_Sort(arr, left, pivot - 1);
                }
                if (pivot + 1 < right) {
                    Quick_Sort(arr, pivot + 1, right);
                }
            }
        }

        // Method to partition the array
        private static int Partition(int[] arr, int left, int right)
        {
            // Select the pivot element
            int pivot = arr[left];

            // Continue until left and right pointers meet
            while (true) 
            {
                // Move left pointer until a value greater than or equal to pivot is found
                while (arr[left] < pivot) 
                {
                    left++;
                }

                // Move right pointer until a value less than or equal to pivot is found
                while (arr[right] > pivot)
                {
                    right--;
                }

                // If left pointer is still smaller than right pointer, swap elements
                if (left < right)
                {
                    if (arr[left] == arr[right]) return right;

                    int temp = arr[left];
                    arr[left] = arr[right];
                    arr[right] = temp;
                }
                else 
                {
                    // Return the right pointer indicating the partitioning position
                    return right;
                }
            }
        }

        static void Main(string[] args)
        {
            int[] arr = new int[] { 2, 5, -4, 11, 0, 18, 22, 67, 51, 6 };

            Console.WriteLine("Original array : ");
            foreach (var item in arr)
            {
                Console.Write(" " + item);    
            }
            Console.WriteLine();

            // Call Quick Sort to sort the array
            Quick_Sort(arr, 0, arr.Length-1);

            Console.WriteLine();
            Console.WriteLine("Sorted array : ");

            foreach (var item in arr)
            {
                Console.Write(" " + item);
            }
            Console.WriteLine();
        }
    }
}

Sample Output:

Original array :                                                                                              
 2 5 -4 11 0 18 22 67 51 6                                                                                    
                                                                                                              
Sorted array :                                                                                                
 -4 0 2 5 6 11 18 22 51 67 
 

Flowchart:

C# Sharp Code Editor:

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