DS-Record-mca-10)AIM:- Write a program for Merge Sort.

 10)AIM:-  Write a program for Merge Sort.

code:-

// Merge sort in C
#include <stdio.h>
#include <conio.h>
// Merge two subarrays L and M into arr
void merge(int arr[], int p, int q, int r)
{
  // Create L ← A[p..q] and M ← A[q+1..r]
  int n1 = q - p + 1;
  int n2 = r - q;
  int L[n1], M[n2];
  for (int i = 0; i < n1; i++)
    L[i] = arr[p + i];
  for (int j = 0; j < n2; j++)
    M[j] = arr[q + 1 + j];
  // Maintain current index of sub-arrays and main array
  int i, j, k;
  i = 0;
  j = 0;
  k = p;
 // Until we reach either end of either L or M, pick larger among
  // elements L and M and place them in the correct position at A[p..r]
  while (i < n1 && j < n2)
  {
    if (L[i] <= M[j])
    {
      arr[k] = L[i];
      i++;
    } else
    {
      arr[k] = M[j];
      j++;
    }
    k++;
  }
  // When we run out of elements in either L or M,
  // pick up the remaining elements and put in A[p..r]
  while (i < n1)
  {
    arr[k] = L[i];
    i++;
    k++;
  }
  while (j < n2)
  {
    arr[k] = M[j];
    j++;
    k++;
  }
}
// Divide the array into two subarrays, sort them and merge them
void mergeSort(int arr[], int l, int r)
{
  if (l < r)
  {
    // m is the point where the array is divided into two subarrays
    int m = l + (r - l) / 2;
    mergeSort(arr, l, m);
    mergeSort(arr, m + 1, r);
    // Merge the sorted subarrays
    merge(arr, l, m, r);
  }
}
// Print the array
void printArray(int arr[], int size)
{
  for (int i = 0; i < size; i++)
    printf("%d ", arr[i]);
  printf("\n");
}
// Driver program
void main()
{
  int arr[] = {6, 5, 12, 10, 9, 1};
  int size = sizeof(arr) / sizeof(arr[0]);
  clrscr();
  mergeSort(arr, 0, size - 1);
  printf("Sorted array: \n");
  printArray(arr, size);
  getch();
}

output:-01