C++ Exercises: Find the missing element from two given arrays of integers except one element

Last update on August 16 2025 12:55:55 (UTC/GMT +8 hours)

22. Find Missing Element from Two Arrays

Write a C++ program to find the missing element from two given arrays of integers except one element.

Sample Solution:

C++ Code :

#include <iostream> // Header file for input/output stream
using namespace std; // Using the standard namespace

int findMissing(int array1[], int array2[], int s1, int s2)
{
    int result = 0; // Initialize a variable to store the missing number using bitwise XOR
    for (int i = 0; i < s1; i++) // Loop through all elements of array1
        result = result ^ array1[i]; // Perform bitwise XOR operation to find the missing number

    for (int i = 0; i < s2; i++) // Loop through all elements of array2
        result = result ^ array2[i]; // Perform bitwise XOR operation to find the missing number

    return result; // Return the missing number found
}

int main()
{
    int array1[] = {3, 1, 5, 7, 9}; // Declaration and initialization of the first array
    int array2[] = {3, 7, 5, 9}; // Declaration and initialization of the second array
    int mn; // Variable to store the missing number
    int s1 = sizeof(array1) / sizeof(array1[0]); // Calculate the size of array1
    int s2 = sizeof(array2) / sizeof(array2[0]); // Calculate the size of array2

    // Check if the difference between the sizes of arrays is not more than 1
    if (s1 != s2 - 1 && s2 != s1 - 1)
    {
        cout << "Invalid Input"; // Print an error message for invalid input
        return 0; // Exit the program
    }

    cout << "Original arrays: "; // Output label for the original arrays

    cout << "\nFirst array: "; // Output label for the first array
    for (int i = 0; i < s1; i++) 
        cout << array1[i] << " "; // Output each element of the first array

    cout << "\nSecond array: "; // Output label for the second array
    for (int i = 0; i < s2; i++) 
        cout << array2[i] << " "; // Output each element of the second array

    mn = findMissing(array1, array2, s1, s2); // Call the function to find the missing number
    cout << "\nMissing number: " << mn; // Output the missing number
    return 0; // Return 0 to indicate successful execution
}

Sample Output:

Original arrays: 
First array: 3 1 5 7 9 
Second array: 3 7 5 9 
Missing number: 1

Flowchart:

For more Practice: Solve these Related Problems:

Write a C++ program to compare two arrays and find the single missing element from the first array that is not in the second.
Write a C++ program that reads two arrays and outputs the element that appears in one array but not in the other using XOR.
Write a C++ program to compute the difference between two arrays and identify the missing number using summation.
Write a C++ program that employs a hash table to compare two arrays and print the element that is missing from one of them.

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