Thread: finding common numbers

I am trying to find the numbers in the two arrays that are in common.

Say they are:

int A[3] = {1, 2, 5};
int B[4] = {1, 5, 9, 10};

Answer should say A \ B = {1, 5}

Code:

#include <stdio.h>

int main (void)
{
    int A[3] = {1, 2, 5};
    int B[4] = {1, 5, 9, 10};

    int x, z;

   for( int x = 0; x < 3; x++ )
    for( int z = 0; z < 4; z++ )

}

I have declared the arrays and I am think the rest is correct.

I'm not sure how to find the common numbers or how to associate the loops with the arrays.

New to C and Arrays.

What you have to do

Two arrays lets say A and B

Code:

    for i = 0  to n - 1 of A
        for j = 0 to n -1 of B
           if value of A[i] == B[j] then add to answer array

before adding to the answer array just check its already there or not

Code:

#include <stdio.h>

int main (void)
{
    int A[3] = {1, 2, 5};
    int B[4] = {1, 5, 9, 10};

    int x, z;

   for( int x = 0; x < 3; x++ )
    for( int z = 0; z < 4; z++ )
        if( A[x] == B[z] )
            printf("A \ B = {%d, %d\n}", A[x], B[z] );

    return 0;
}

My output: A \ B = {1,1}
A \ B = {5, 5}

The numbers are correct.

What's wrong.

Ahh, makes since.

So

Code:

 printf("A \ B = {%d}", A[x] );

Why is it printing it twice?

It doing this, I dont understand it.

A \ B = {1,1}
A \ B = {5, 5}

Im wanting jusr A \ B = {1, 5}

Originally Posted by iMalc

If A and B each held 10000 numbers or more, would you still use the same algorithm?

The arrays are sorted. If it's a safe assumption that they are always sorted then there's a much quicker approach. Try studying the C++ standard library code for set_intersection.

Can we also assume there are no duplicates?

Ok iMac Please tell me if the numbers are unsorted then the algo

Originally Posted by laserlight

... would be to sort them and then use an algorithm that works when they are sorted.

So how many compressions will be there less the one above of yours or more ????
And which will be faster

Originally Posted by laserlight

I think you mean "comparisons" instead of "compressions". Unfortunately, I do not really understand your sentence. What algorithms are you trying to compare?

Then without knowing the algo how can u write

Quote:
Originally Posted by RockyMarrone
Ok iMac Please tell me if the numbers are unsorted then the algo
... would be to sort them and then use an algorithm that works when they are sorted.

I figured it out.

Thanks for the help.