# C# - Sorting Algorithm - Merge Sort Recursive

We often using sorting algorithm to sort numbers and strings. Also we have many sorting algorithms. I have explained here on how merge sort algorithm works in recursive mode.

The recusrive approach requires creatiion multi branch recursion until the elements are comparable by one iterm. The the merging happens with DoMerge function by taking three arguments - start, mid and right.

The complete program and test run output are given below:

## Source Code

using System;

using System.Collections.Generic;

using System.Text;

namespace CSharpSort

{

class Program

{

static public void DoMerge(int [] numbers, int left, int mid, int right)

{

int [] temp = new int;

int i, left_end, num_elements, tmp_pos;

left_end = (mid - 1);

tmp_pos = left;

num_elements = (right - left + 1);

while ((left <= left_end) && (mid <= right))

{

if (numbers[left] <= numbers[mid])

temp[tmp_pos++] = numbers[left++];

else

temp[tmp_pos++] = numbers[mid++];

}

while (left <= left_end)

temp[tmp_pos++] = numbers[left++];

while (mid <= right)

temp[tmp_pos++] = numbers[mid++];

for (i = 0; i < num_elements; i++)

{

numbers[right] = temp[right];

right--;

}

}

static public void MergeSort_Recursive(int [] numbers, int left, int right)

{

int mid;

if (right > left)

{

mid = (right + left) / 2;

MergeSort_Recursive(numbers, left, mid);

MergeSort_Recursive(numbers, (mid + 1), right);

DoMerge(numbers, left, (mid+1), right);

}

}

static void Main(string[] args)

{

int[] numbers = { 3, 8, 7, 5, 2, 1, 9, 6, 4 };

int len = 9;

Console.WriteLine("MergeSort By Recursive Method");

MergeSort_Recursive(numbers, 0, len - 1);

for (int i = 0; i < 9; i++)

Console.WriteLine(numbers[i]);

Console.WriteLine(numbers[i]);

}

}

}

## Output

MergeSort By Recursive Method

1

2

3

4

5

6

7

8

9

Press any key to continue . . .