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

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
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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); ` `  ``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

 ` `

Output

```The missing element : 30
```

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