# Find Union and Intersection of two unsorted arrays in C++

In this tutorial, we are going to learn how to write a program for union and intersection of two unsorted arrays. Let's see an example.

Input

arr_one = [1, 2, 3, 4, 5]
arr_two = [3, 4, 5, 6, 7]

Output

union: 1 2 3 4 5 6 7
intersection: 3 4 5

Let's see the steps to solve the problem.

## Union

• Initialize the two arrays with random values.

• Create an empty array called union_result.

• Iterate over the first array and add every element to it.

• Iterate over the section array and add element if it is not present in union_result array.

• Print the union_result array.

## Intersection

• Initialize the two arrays with random values.

• Create an empty array called intersection_result.

• Iterate over the first array and add element if it is present in second array.

• Print the intersection_result array.

## Example

See the code below

Live Demo

#include <bits/stdc++.h>
using namespace std;
int isElementPresentInArray(int arr[], int arr_length, int element) {
for (int i = 0; i < arr_length; ++i) {
if (arr[i] == element) {
return true;
}
}
return false;
}
void findUnionAndIntersection(int arr_one[], int arr_one_length, int arr_two[], int arr_two_length) {
// union
int union_result[arr_one_length + arr_two_length] = {};
for (int i = 0; i < arr_one_length; ++i) {
union_result[i] = arr_one[i];
}
int union_index = arr_one_length;
for (int i = 0; i < arr_two_length; ++i) {
if (!isElementPresentInArray(arr_one, arr_one_length, arr_two[i])) {
union_result[union_index++] = arr_two[i];
}
}
cout << "Union: ";
for (int i = 0; i < union_index; ++i) {
cout << union_result[i] << " ";
}
cout << endl;
// intersection
int intersection_result[arr_one_length + arr_two_length] = {};
int intersection_index = 0;
for (int i = 0; i < arr_one_length; ++i) {
if (isElementPresentInArray(arr_two, arr_two_length, arr_two[i])) {
intersection_result[intersection_index++] = arr_one[i];
}
}
cout << "Intersection: ";
for (int i = 0; i < intersection_index; ++i) {
cout << intersection_result[i] << " ";
}
cout << endl;
}
int main() {
int arr_one[] = {1, 2, 3, 4, 5};
int arr_two[] = {3, 4, 5, 6, 7};
findUnionAndIntersection(arr_one, 5, arr_two, 5);
return 0;
}

## Output

If you execute the above program, then you will get the following result.

Union: 1 2 3 4 5 6 7
Intersection: 1 2 3 4 5

## Conclusion

If you have any queries in the tutorial, mention them in the comment section.