# Total number of subsets in which the product of the elements is even

Given an array arr[] of integer elements, the task is to find the total number of sub-sets of arr[] in which product of the elements is even.

Examples:

Input: arr[] = {2, 2, 3}
Output: 6
All possible sub-sets are {2}, {2}, {2, 2}, {2, 3}, {2, 3} and {2, 2, 3}

Input: arr[] = {3, 3, 3}
Output: 0

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

Approach: We already know that :

• Even * Even = Even
• Odd * Even = Even
• Odd * Odd = Odd

Now, we need to count the total subsets in which at least a single even element is present in order for the product of the elements to be even.
Now, Total number of sub-sets having at least one even element = Total possible sub-sets of n – Total sub-sets having all odd elements
i.e. (2n – 1) – (2totalOdd – 1)

Below is the implementation of the above approach:

## C++

 `// C++ implementation of above approach ` ` `  `#include ` `#include ` ` `  `using` `namespace` `std; ` ` `  `// Function to find total number of subsets  ` `// in which product of the elements is even ` `void` `find(``int` `a[], ``int` `n) ` `{ ` `    ``int` `count_odd = 0; ` `     `  `    ``for``(``int` `i = 0; i < n ; i++) ` `    ``{ ` `        ``// counting number of odds elements ` `        ``if` `(i % 2 != 0) ` `        ``count_odd += 1; ` `    ``} ` ` `  `    ``int` `result = ``pow``(2, n) - 1 ; ` `    ``result -= (``pow``(2, count_odd) - 1) ; ` `    ``cout << result << endl; ` `     `  `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `   ``int` `a[] = {2, 2, 3} ; ` `   ``int` `n = ``sizeof``(a)/``sizeof``(a) ; ` `    `  `   ``// function calling ` `   ``find(a,n); ` `    `  `   ``return` `0; ` `   ``// This code is contributed by ANKITRAI1; ` `} `

## Java

 `// Java implementation of above approach  ` ` `  `class` `GFG { ` ` `  `// Function to find total number of subsets  ` `// in which product of the elements is even  ` `    ``static` `void` `find(``int` `a[], ``int` `n) { ` `        ``int` `count_odd = ``0``; ` ` `  `        ``for` `(``int` `i = ``0``; i < n; i++) { ` `            ``// counting number of odds elements  ` `            ``if` `(i % ``2` `!= ``0``) { ` `                ``count_odd += ``1``; ` `            ``} ` `        ``} ` ` `  `        ``int` `result = (``int``) (Math.pow(``2``, n) - ``1``); ` `        ``result -= (Math.pow(``2``, count_odd) - ``1``); ` `        ``System.out.println(result); ` ` `  `    ``} ` ` `  `// Driver code  ` `    ``public` `static` `void` `main(String[] args) { ` `        ``int` `a[] = {``2``, ``2``, ``3``}; ` `        ``int` `n = a.length; ` ` `  `// function calling  ` `        ``find(a, n); ` ` `  `    ``} ` `} ` `//this code contributed by 29AJayKumar `

## Python3

 `# Python3 implementation of above approach ` `import` `math as ma ` ` `  `# Function to find total number of subsets  ` `# in which product of the elements is even ` `def` `find(a): ` `    ``count_odd ``=` `0` `    ``for` `i ``in` `a: ` ` `  `        ``# counting number of odds elements ` `        ``if``(i ``%` `2` `!``=` `0``): ` `            ``count_odd``+``=` `1` ` `  `    ``result ``=` `pow``(``2``, ``len``(a)) ``-` `1` `    ``result ``=` `result ``-` `(``pow``(``2``, count_odd) ``-` `1``) ` `    ``print``(result) ` ` `  `# Driver code ` `a ``=``[``2``, ``2``, ``3``] ` `find(a) `

## C#

 `     `  `// C# implementation of above approach  ` `using` `System; ` `public` `class` `GFG { ` `  `  `// Function to find total number of subsets  ` `// in which product of the elements is even  ` `    ``static` `void` `find(``int` `[]a, ``int` `n) { ` `        ``int` `count_odd = 0; ` `  `  `        ``for` `(``int` `i = 0; i < n; i++) { ` `            ``// counting number of odds elements  ` `            ``if` `(i % 2 != 0) { ` `                ``count_odd += 1; ` `            ``} ` `        ``} ` `  `  `        ``int` `result = (``int``) (Math.Pow(2, n) - 1); ` `        ``result -= (``int``)(Math.Pow(2, count_odd) - 1); ` `        ``Console.Write(result); ` `  `  `    ``} ` `  `  `// Driver code  ` `    ``public` `static` `void` `Main() { ` `        ``int` `[]a = {2, 2, 3}; ` `        ``int` `n = a.Length; ` `  `  `// function calling  ` `        ``find(a, n); ` `  `  `    ``} ` `} ` `//this code contributed by 29AJayKumar `

## PHP

 ` `

Output:

```6
```

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