C Program to Find Union and Intersection of Two Arrays

This C program finds the union and intersection of two arrays. It takes two arrays as input and computes the resulting union and intersection arrays.

Program Statement

Here’s the program statement for the C program to find the union and intersection of two arrays:

Program Statement:

Write a C program to find the union and intersection of two arrays. The program should take two input arrays arr1 and arr2 of integers, along with their sizes n1 and n2 respectively. The program should then find and print the union of the two arrays, followed by the intersection of the two arrays.

Input:

• Two input arrays arr1 and arr2 of integers.
• The size of arr1, denoted by n1.
• The size of arr2, denoted by n2.

Output:

• The union of arr1 and arr2, without any duplicates.
• The intersection of arr1 and arr2, containing only the common elements.

C Program to Find Union and Intersection of Two Arrays

#include <stdio.h>

void findUnion(int arr1[], int arr2[], int m, int n) {
    int i = 0, j = 0;
    while (i < m && j < n) {
        if (arr1[i] < arr2[j])
            printf("%d ", arr1[i++]);
        else if (arr2[j] < arr1[i])
            printf("%d ", arr2[j++]);
        else {
            printf("%d ", arr2[j++]);
            i++;
        }
    }

    while (i < m)
        printf("%d ", arr1[i++]);

    while (j < n)
        printf("%d ", arr2[j++]);
}

void findIntersection(int arr1[], int arr2[], int m, int n) {
    int i = 0, j = 0;
    while (i < m && j < n) {
        if (arr1[i] < arr2[j])
            i++;
        else if (arr2[j] < arr1[i])
            j++;
        else {
            printf("%d ", arr2[j++]);
            i++;
        }
    }
}

int main() {
    int arr1[] = {1, 2, 4, 5, 6};
    int arr2[] = {2, 3, 5, 7};

   int m = sizeof(arr1) / sizeof(arr1[0]);
    int n = sizeof(arr2) / sizeof(arr2[0]);

    printf("Union: ");
    findUnion(arr1, arr2, m, n);

    printf("\nIntersection: ");
    findIntersection(arr1, arr2, m, n);

    return 0;
}

How it works

Let me explain how the program works step by step:

1. In the main function, two arrays arr1 and arr2 are defined, along with their respective sizes n1 and n2. The example arrays are:cssCopy codearr1 = [1, 2, 4, 5, 6] arr2 = [2, 3, 5, 7]
2. The findUnion function is called with arr1, n1, arr2, and n2 as arguments. This function finds and prints the union of the two arrays.
3. Inside the findUnion function, two variables i and j are initialized to 0. These variables are used as indices to iterate over arr1 and arr2 respectively.
4. The function enters a loop that continues as long as i is less than n1 (the size of arr1) and j is less than n2 (the size of arr2).
5. Within the loop, the function compares the elements of arr1[i] and arr2[j]:
   • If arr1[i] is less than arr2[j], it means arr1[i] is not present in arr2. So, the element arr1[i] is printed as part of the union, and i is incremented to move to the next element in arr1.
   • If arr2[j] is less than arr1[i], it means arr2[j] is not present in arr1. So, the element arr2[j] is printed as part of the union, and j is incremented to move to the next element in arr2.
   • If arr1[i] is equal to arr2[j], it means the element is common to both arrays. So, the element is printed as part of the union, and both i and j are incremented to move to the next elements in both arrays.
6. After the loop ends, there may be some remaining elements in either arr1 or arr2. The function uses two separate while loops to print any remaining elements in arr1 and arr2, if any.
7. The findIntersection function is called with the same arguments as the findUnion function. This function finds and prints the intersection of the two arrays.
8. Inside the findIntersection function, a similar comparison loop is used to iterate over arr1 and arr2. However, instead of printing elements, the function only increments i and j when the elements are not equal. When the elements are equal, it means the element is common to both arrays, so it is printed as part of the intersection.
9. Finally, the main function prints the output by calling the printf function. The union is printed first by calling findUnion, followed by the intersection, which is printed by calling findIntersection.

That’s how the program works! It compares the elements of the two arrays and determines the union and intersection based on the comparison results.

Input/Output