Implementation of Merge Sort

AIM:

          To write a C program to implement Merge sort

ALGORITHM:

            Step 1: Start the program.

Step 2: To sort A[p .. r]: Divide Step: If a given array A has zero or one element,

simply return; it is already sorted. Otherwise, split A[p .. r] into two

sub arrays A[p .. q] and A[q + 1 .. r], each containing about half of the

elements of A[p .. r]. That is, q is the halfway point of A[p .. r].

Step 3: Conquer Step: Conquer by recursively sorting the two sub arrays A[p .. q]

            and A[q + 1 .. r].

Step 4: Combine Step : Combine the elements back in A[p .. r] by merging the

            two sorted sub arrays A[p .. q] and A[q + 1 .. r] into a sorted sequence. To

            accomplish this step, we will define a procedure MERGE (A, p, q, r).

Step 5: Stop the program.

PROGRAM

#include<stdio.h>

#define MAX 50

void mergeSort(int arr[],int low,int mid,int high);

void partition(int arr[],int low,int high);

int main()

{

int merge[MAX],i,n;

printf("Enter the total number of elements: ");

scanf("%d",&n);

printf("Enter the elements which to be sort: ");

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

{

scanf("%d",&merge[i]);

}

partition(merge,0,n-1);

printf("After merge sorting elements are: ");

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

{

printf("%d ",merge[i]);

}

return 0;

}

void partition(int arr[],int low,int high){

int mid;

if(low<high)

{

mid=(low+high)/2;

partition(arr,low,mid);

partition(arr,mid+1,high);

mergeSort(arr,low,mid,high);

}

}

void mergeSort(int arr[],int low,int mid,int high)

{

int i,m,k,l,temp[MAX];

l=low;

i=low;

m=mid+1;

while((l<=mid)&&(m<=high))

{

if(arr[l]<=arr[m])

{

temp[i]=arr[l];

l++;

}

else

{

temp[i]=arr[m];

m++;

}

i++;

}

if(l>mid)

{

for(k=m;k<=high;k++)

{

temp[i]=arr[k];

i++;

}

}

else

{

for(k=l;k<=mid;k++){

temp[i]=arr[k];

i++;

}

}

for(k=low;k<=high;k++)

{

arr[k]=temp[k];

}

}

OUTPUT

Enter the total number of elements: 5

Enter the elements which to be sort: 2 5 0 9 1

After merge sorting elements are: 0 1 2 5 9

  

RESULT: Thus a C program is written to implement merge sort and executed

                  successfully