/* prg to implement circular convolution */
#include<stdio.h>
   int m,n,x[30],h[30],y[30],i,j,temp[30],k,x2[30],a[30];
void main()
{


   printf("  enter the length of the first sequence\n");
   scanf("%d",&m);
   printf("  enter the length of the second sequence\n");
   scanf("%d",&n);
   printf("  enter the first sequence\n");
   for(i=0;i<m;i++)
   scanf("%d",&x[i]);
   printf("  enter the second sequence\n");
   for(j=0;j<n;j++)
   scanf("%d",&h[j]);
   if(m-n!=0)				/*Iflenght of both sequences are not equal*/
   {
	if(m>n)					/* Pad the smaller sequence with zero*/
	{
	for(i=n;i<m;i++)
	h[i]=0;
	n=m;
	}
	for(i=m;i<n;i++)
	x[i]=0;
	m=n;
   }

   y[0]=0;
   a[0]=h[0];
   for(j=1;j<n;j++)					/*folding h(n) to h(-n)*/
   a[j]=h[n-j];

   /*Circular convolution*/
  for(i=0;i<n;i++)
   y[0]+=x[i]*a[i];
  for(k=1;k<n;k++)
  {
   y[k]=0;
   /*circular shift*/
   for(j=1;j<n;j++)
	x2[j]=a[j-1];

   x2[0]=a[n-1];
   for(i=0;i<n;i++)
    {
	a[i]=x2[i];
	y[k]+=x[i]*x2[i];
    }
 }
  /*displaying the result*/
  printf("  the circular convolution is\n");
  for(i=0;i<n;i++)
  printf("%d \t",y[i]);

  }