In this program, You will learn how to find union and intersection of two arrays in C++.

```
The first list is: 1 2 3 4 5
The second list is: 3 4 5
Union is: 1 2 3 4 5
Intersection is: 3 4 5
```

## Example: How to find union and intersection of two arrays in C++.

```
#include<iostream>
using namespace std;
void printUnion(int arr1[], int arr2[], int len1, int len2) {
int f, i, j, k = 0;
int arr3[100];
for (i = 0; i < len1; i++) {
arr3[k] = arr1[i];
k++;
}
for (i = 0; i < len2; i++) {
f = 0;
for (j = 0; j < len1; j++) {
if (arr2[i] == arr1[j]) {
f = 1;
}
}
if (f == 0) {
arr3[k] = arr2[i];
k++;
}
}
cout << "Union of two array is:";
for (i = 0; i < k; i++) {
cout << arr3[i] << " ";
}
}
void printIntersection(int arr1[], int arr2[], int len1, int len2) {
int arr3[100];
int i, j, k = 0;
for (i = 0; i < len1; i++) {
for (j = 0; j < len2; j++) {
if (arr1[i] == arr2[j]) {
arr3[k] = arr1[i];
k++;
}
}
}
cout << "\nIntersection of two array is:";
for (i = 0; i < k; i++) {
cout << arr3[i] << " ";
}
}
int main() {
int arr1[100];
int arr2[100];
int arr3[100];
int i, j, len1, len2;
cout << "Enter size of 1st array:";
cin>>len1;
cout << "Enter 1st array elements:";
for (i = 0; i < len1; i++) {
cin >> arr1[i];
}
cout << "Enter size of 2nd array:";
cin>>len2;
cout << "Enter 2nd array elements:";
for (i = 0; i < len2; i++) {
cin >> arr2[i];
}
printUnion(arr1, arr2, len1, len2);
printIntersection(arr1, arr2, len1, len2);
return 0;
}
```

#### Output:

```
Enter size of 1st array:4
Enter 1st array elements:10 20 30 40
Enter size of 2nd array:3
Enter 2nd array elements:30 40 50
Union of two array is:10 20 30 40 50
Intersection of two array is:30 40
```