/*
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ASSIGNMENT NO : 6
TITLE : WRITE A PROGRAM IN C TO FIND CIRCULAR CONVOLUTION OF TWO SEQUENCES.
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*/
#include<stdio.h>
#include<conio.h>
int m,n,x[30],h[30],y[30],i,j, k,x2[30],a[30];
void main()
{
clrscr();
printf("\\n Enter the length of the first sequence = ");
scanf("%d",&m);
printf("\\n Enter the length of the second sequence = ");
scanf("%d",&n);
printf("\\nEnter the first sequence = ");
for(i=0;i<m;i++)
scanf("%d",&x[i]);
printf("\\nEnter the second sequence = ");
for(j=0;j<n;j++)
scanf("%d",&h[j]);
if(m-n!=0) /*If length 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(" \\nThe circular convolution = ");
for(i=0;i<n;i++)
printf("%d \\t",y[i]);
getch();
}