clc
clear all;
close all;

x = input('enter the sequence :');
px=input('pointer position of x : ');
a = input('enter the impulse sequence :');
ph=input('pointer position of h : ');
for i= 1:length(a)
    h(i) = a(length(a)+1-i);
end
lx=length(x);
lh=length(h);
left=1-px;
right=lx-px;
left1=-(lh-ph);
right1=-(1-ph);

t=[left:right];
t1=[left1:right1];

subplot(3,1,1)
stem(t,x)
title('input sequence(x)')
subplot(3,1,2)
stem(t1,a)
title('input sequence(h)')

for i= 1:lh
    ph(i) = h(lh+1-i);
end
t3=[-right1:-left1];
x1 = [zeros(1,lh-1), x , zeros(1, lh-1)];
ly = lx+lh-1;
for i = 1:ly
    z = x1(1, 1:length(ph)) .*ph;
    y(i) = sum(z);
    ph = [ 0 ph];
end
y
t4 = [left+left1:right+right1];
subplot(3,1,3)
stem(t4,y)
if(x==a)
    title('auto-corelation signal(y)')
else
    title('cross-corelation signal(y)')
end