Intersection of 2 arrays

**Cazan Adelin** · 01-13-2015

Hello guys, I've been watching this forum for the past 2 weeks and I can say you do a nice job here.
I know this have been posted a million times, but i still can't solve my problem.

Code:

#define _CRT_SECURE_NO_WARNINGS#include <stdio.h>
#include <stdlib.h>


int main()


{
    int a[10],b[10],c[10],i,j,k,n,m;
    printf ("Enter the size of the first vector: ");
    scanf ("%d", &n);
    for ( i=0 ; i<n ; i++)
    {
        printf ("a[%d]= ", i);
        scanf ("%d", &a[i]);
    }
    printf ("Enter the size of the second vector: ");
    scanf ("%d", &m);
    for ( j=0 ; j<m ; j++)
    {
        printf ("b[%d]= ", j);
        scanf ("%d", &b[i]);
    }
    if ( a[i] == b[j] )
    {
        printf ("a[%d]", i);
    }
    system("pause");
}

Now, this is what I've been able to do so far, i know it's very basic but I just started learning programming! I tried different methods found on internet but none of them work for me. I want to find the intersection of arrays a & b then put them in array c(or just display them?)

Thanks in advance!

**laserlight** · 01-13-2015

What is your idea for solving this?

**Cazan Adelin** · 01-13-2015

I was thinking of making a for
(a[i] == b[j])
then copy a[i] into c[k] or something like that, I'm not sure if it's possible...
Or if it's the best way...

**laserlight** · 01-13-2015

You are heading in a right direction. What you need are nested loops.

It wouldn't be the most efficient way, but that can come later.

**Cazan Adelin** · 01-13-2015

Should i check for "nested loops" and inform about them then try to implement ?
Or find a more efficient way ?

I appreciate the help, and i know it's better to find this out on my own... But I'm not sure I can, i'm a real newbie

So if you could give me and example and a little explanation so i could try and understand it, it would be great!

Thanks again for your time !

**WoodSTokk** · 01-13-2015

You have a mistake on line 22. The loop is counting 'j', but you set 'b[i]'.

The user enter the size on line 10/11 and 17/18, but you don't check if the value is greater then 10.
If the user enter a higher value, your loops overrun the array bounderies.

The main-function should return a integer.
Your function definition is right, but you have no 'return 0;' at end of the function.

**laserlight** · 01-13-2015

Originally Posted by Cazan Adelin

Should i check for "nested loops" and inform about them then try to implement ?

A nested loop just means that it is a loop within another loop. In this case, the outer loop will loop over one array, and the inner loop will loop over the other array to check for a match.

Originally Posted by Cazan Adelin

Or find a more efficient way ?

If you want an efficient method, then sort the two arrays. Once the arrays are sorted, you can iterate over them in parallel, copying over to the third array only those elements that have the same value.

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