merge sort

#include<stdio.h>
#include<conio.h>
#include<time.h>
#include<dos.h>
int a[20],b[20];
int n;
void mergsort(int low, int high);
void merge(int low, int mid, int high);
void main()
{
int i;
clock_t start, end;
clrscr();
printf(" Enter size of an array: ");
scanf("%d",&n);
printf("\n Enter %d integers. : ",n);
for(i=0;i<n;i++)
scanf("%d",&a[i]);
printf("\n");
start = clock();
mergsort(0,n-1);
printf("\n\n\n Sorted list: ");
for(i=0;i<n;i++)
printf("%3d",a[i]);
end = clock();
printf("\n Total time = %f seconds",(end-start)/CLK_TCK);
getch();
}

2

// Divide the task
void mergsort(int low, int high)
{
int mid;
if(low<high)
{
mid = (low+high)/2;
mergsort(low,mid);
mergsort(mid+1,high);
merge(low,mid,high);
}
}
//Merge sorted lists
void merge(int low, int mid, int high)
{
int h,i,j,k;
h = low; // Varies from low to mid
j=mid+1; // Varies from mid+1 to high
i=low; // Varies from low to high
while((h<=mid) && (j<=high))
{
if(a[h]<=a[j])
{

b[i]=a[h]; // Insert Element from left
list to sorted list

h++;
}
else
{
b[i]=a[j]; // Insert Element from right to sorted list
j++;
}
i++; // Update index of sorted list
}

3

if(h>mid) // Left list get terminated
for(k=j;k<=high;k++)
{
b[i]=a[k]; //Append elements from right list to sorted list
i++;
}
else // Right list get terminated
for(k=h;k<=mid;k++)
{
b[i]=a[k]; // Append elements from left list to sorted list
i++;
}
printf("\n");
for(k=low;k<=high;k++) // Display passes
{
a[k]=b[k];
printf("%5d ",a[k]);
}
}