C++ program to find the union and intersection of two arrays

Here are C++ programs to find the union and intersection of two arrays. First program finds union of two arrays and second program finds intersection of two arrays.

C++ program to find the union of two arrays

#include<iostream>
using namespace std;
int main()
{
    int a1[20],a2[20],k=0,num,unio[40],flag=0;
    cout<<"How many elements to be stored (max 20) : ";
    cin>>num;
    cout<<"Enter elements of array a1 : ";
    for(int i=0;i<num;i++,k++)
    {
        cin>>a1[i];
        unio[k]=a1[i];
    }
    cout<<"Enter elements of array a2 : ";
    for(int i=0;i<num;i++,k++)
    {
        cin>>a2[i];
        unio[k]=a2[i];
    }
    cout<<"a1 union a2 : ";
    for(int i=0;i<k;i++)
    {
       for(int y=i+1;y<k;y++)
            if(unio[i]==unio[y])
                 flag=1;
       if(flag==0)
           cout<<unio[i]<<" ";
       flag=0;
    }
    return 0;
}

OUTPUT

C++ program to find the  intersection of two arrays

#include<iostream>
using namespace std;
int main()
{
    int a1[20],a2[20],intersec[40],k=0,num,flag=0;
    cout<<"How many elements to be stored (max 20) : ";
    cin>>num;
    cout<<"Enter elements of array a1 : ";
    for(int i=0;i<num;i++)
       cin>>a1[i];
    cout<<"Enter elements of array a2 : ";
    for(int i=0;i<num;i++)
       cin>>a2[i];
    for(int i=0;i<num;i++)
    {
        for(int y=0;y<num;y++)
            if(a1[i]==a2[y])
                intersec[k++]=a1[i];

    }
    cout<<"a1 intersection a2 : ";
    for(int i=0;i<k;i++)
    {
       for(int y=i+1;y<k;y++)
            if(intersec[i]==intersec[y])
                 flag=1;
       if(flag==0)
           cout<<intersec[i]<<" ";
       flag=0;
    }
    return 0;
}

OUTPUT