# Find the missing number in an array using C#, Python, Java, and C with code examples.

An array is a collection of similar data types stored in contiguous memory locations.

In this article, we will discuss how to find the missing number in an array of 1 to 10 using C#, Python, Java, and C programming languages.

### C# program to find the missing number in an array of 1 to 10

We will create an array with numbers 1 to 10 where number 5 is missing in the sequence.

Tips:

We can calculate the sum of the numbers within the range [1, N] using the formula `N * (N + 1)/2`.
Subsequently, we need to find the sum of the elements in the array and subtract this sum from the previously calculated sum of the first N natural numbers.
The result will give you the value of the missing element.

``````using System;

class Find_Missing_Number
{
static void Main (string [] args)
{
//array to find the missing number between 1 and 10
// We will take number 1 to 10 where number 5 is missing in the sequence.
int [] arr = { 1, 2, 3, 4, 6, 7, 8, 9, 10 };

int missingNumber, Totalsum;
// According to series rule, calculating sum of total numbers up to 10
//sum of first n natutal numbers=n* (n+1)/2

Totalsum = (arr.Length + 1) * (arr.Length + 2) / 2;
// Missing number is calculating.
foreach (int item in arr)
{
Totalsum = Totalsum - item;
}
missingNumber = Totalsum;
Console.WriteLine (\$"Missing Number in C#: {missingNumber}");
}
}
``````

Result:

``Missing Number in C#: 5``

Code explanation:

1. The `Totalsum` variable is calculated using the formula for the sum of the first n natural numbers: `(arr.Length + 1) * (arr.Length + 2) / 2`.
2. The code then iterates through each element in the array and subtracting it from `Totalsum`.
3. The result is the missing number, which we are printing to the console.

### Python program to find the missing number in an integer array of 1 to 10

``````def find_missing_number_python(numbers):
expected_sum = 10 * (10 + 1) // 2
actual_sum = sum(numbers)
return expected_sum - actual_sum

numbers = [1, 2, 3, 4, 6, 7, 8, 9, 10]
missing_number = find_missing_number_python(numbers)
print(f"Missing Number in Python: {missing_number}")``````

Result:

``Missing Number in Python: 5``

### Java program to find the missing number in an integer array of 1 to 10

``````public class MissingNumberJava {
public static void main(String[] args) {
int[] numbers = {1, 2, 3, 4, 6, 7, 8, 9,10};
int missingNumber = findMissingNumberJava(numbers);

System.out.println("Missing Number in Java: " + missingNumber);
}

static int findMissingNumberJava(int[] arr) {
int expectedSum = 10 * (10 + 1) / 2;
int actualSum = 0;
for (int num : arr) {
actualSum += num;
}
return expectedSum - actualSum;
}
}
``````

Result:

``Missing Number in Java: 5``

### C program to find the missing number in an integer array of 1 to 10

In this C Program, we will create an array with numbers 1 to 10 where number 5 is missing in the sequence.

``````#include <stdio.h>

int find_missing_number_c(int numbers[], int length) {
int expected_sum = (length + 1) * (length + 2) / 2;
int actual_sum = 0;

for (int i = 0; i < length; i++) {
actual_sum += numbers[i];
}

return expected_sum - actual_sum;
}

int main() {
int numbers[] = {1, 2, 3, 4, 6, 7, 8, 9, 10};
int length = sizeof(numbers) / sizeof(numbers[0]);

int missing_number = find_missing_number_c(numbers, length);

printf("Missing Number in C: %d\n", missing_number);

return 0;
}
``````

Result:

``Missing Number in C: 5``

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