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C program to find the missing number in the array

Here, we are going to learn how to find the missing number in the array in C programming language?
Submitted by Nidhi, on July 11, 2021

Problem Solution:

Here, we will create an array of integers then we will find the missing number from the array.

Program:

The source code to find the missing number in the array is given below. The given program is compiled and executed using GCC compile on UBUNTU 18.04 OS successfully.

// C program to find the missing number in the array

#include <stdio.h>

int main()
{
    int arr[] = { 1, 2, 3, 5, 6 };

    int size = 0;
    int i = 0;
    int missing = 0;

    size = sizeof(arr) / sizeof(arr[0]);

    missing = (size + 1) * (size + 2) / 2;

    for (i = 0; i < size; i++)
        missing = missing - arr[i];

    printf("Missing number is: %d\n", missing);

    return 0;
}

Output:

Missing number is: 4

Explanation:

Here, we created an array arr with 5 elements. And, we also created three variables size, missing, i that are initialized with 0. Then we found missing elements from the array and printed the result on the console screen.

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