# Find the missing integer in an array if mean is given

• Difficulty Level : Basic
• Last Updated : 29 Apr, 2021

Given an array of size N-1 and the mean of N elements (one element is not given). We need to find the missing value X in the array.
Examples:

```Input : a[] = {2, 4, 20}
Mean = 9
Output : Missing Element = 10
Explanation : Mean of (2, 4, 20, 10) is
(2 + 4 + 20 + 10)/4 = 9```

Let x be the missing element
Mean = (a1 + a2 + a3.. + X + ..an)/N.
So (a1 + a2 + a3.. + X + ..aN) = Mean*N .
Missing element x = (Mean*N – (a1 + a2 + a3….aN))

## C++

 `// C++ program to find missing element in a``// given array from mean.``#include ``using` `namespace` `std;` `// Size of a[] is N - 1 (one element missing)``int` `findMissing(``int` `a[], ``int` `N, ``int` `mean)``{``  ``// Find sum of array elements``  ``int` `sum = 0;``  ``for` `(``int` `i = 0; i < N - 1; i++)``    ``sum += a[i]; ` `  ``return` `(mean * N) - sum;``}` `int` `main() {``  ``int` `a[] = {25, 65, 80};``  ``int` `mean = 50;``  ``int` `n = ``sizeof``(a)/``sizeof``(a[0]);``  ``cout << ``"The missing element : "``       ``<< findMissing(a, n+1, mean)  << endl;``  ``return` `0;``}`

## Java

 `// Java program to find missing element``// in a given array from mean.``import` `java.io.*;` `class` `GFG``{``    ``// Size of a[] is N - 1 (one element missing)``    ``public` `static` `int` `findMissing(``int` `a[], ``int` `N, ``int` `mean)``    ``{``        ``// Find sum of array elements``        ``int` `sum = ``0``;``        ``for` `(``int` `i = ``0``; i < N - ``1``; i++)``        ``sum += a[i];` `        ``return` `(mean * N) - sum;``    ``}``    ` `    ``// Driver code``    ``public` `static` `void` `main (String[] args)``    ``{``        ``int` `a[] = {``25``, ``65``, ``80``};``        ``int` `mean = ``50``;``        ``int` `n = a.length;``        ``System.out.println(``"The missing element : "``                           ``+ findMissing(a, n + ``1``, mean));``        ` `    ``}``}` `// This code is contributed by upendra bartwal`

## Python3

 `# Python3 code to find missing element``# in a given array from mean.` `# Size of a[] is N - 1``# (one element missing)``def` `findMissing( a , N , mean ):` `    ``# Find sum of array elements``    ``sum` `=` `0``    ``for` `i ``in` `range``(N ``-` `1``):``        ``sum` `+``=` `a[i]``    ` `    ``return` `(mean ``*` `N) ``-` `sum` `# Driver Code``a ``=` `[``25``, ``65``, ``80``]``mean ``=` `50``n ``=` `len``(a)``print``(``"The missing element : "``, end ``=` `'')``print``(findMissing(a, n``+``1``, mean))` `# This code is contributed by Sharad Bhardwaj.`

## C#

 `// C# program to find missing element``// in a given array from mean.``using` `System;` `class` `GFG {``    ` `    ``// Size of a[] is N - 1``    ``// (one element missing)``    ``public` `static` `int` `findMissing(``int``[] a, ``int` `N, ``int` `mean)``    ``{``        ` `        ``// Find sum of array elements``        ``int` `sum = 0;``        ``for` `(``int` `i = 0; i < N - 1; i++)``            ``sum += a[i];` `        ``return` `(mean * N) - sum;``    ``}` `    ``// Driver code``    ``public` `static` `void` `Main()``    ``{``        ``int``[] a = { 25, 65, 80 };``        ``int` `mean = 50;``        ``int` `n = a.Length;``        ``Console.WriteLine(``"The missing element : "``                    ``+ findMissing(a, n + 1, mean));``    ``}``}` `// This code is contributed by vt_m.`

## PHP

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## Javascript

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Output:

`The missing element : 30`

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