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# Product of Primes of all Subsets

• Last Updated : 18 May, 2021

Given an array a[] of size N. The value of a subset is the product of primes in that subset. A non-prime is considered to be 1 while finding value by-product. The task is to find the product of the value of all possible subsets.
Examples:

Input: a[] = {3, 7}
Output: 20
The subsets are: {3} {7} {3, 7}
{3, 7} = 3 * 7 = 21
{3} = 3
{7} = 7
21 * 3 * 7 = 441
Input: a[] = {10, 2, 14, 3}
Output: 1679616

Naive Approach: A naive approach is to find all the subsets using power set and then find the product by multiplying all the values of the subset. Prime can be checked using Sieve
Time Complexity: O(2N)
Efficient Approach: An efficient approach is to solve the problem using observation. If we write all the subsequences, a common point of observation is that each number appears 2(N – 1) times in a subset and hence will lead to the 2(N-1) as the contribution to the product. Iterate through the array and check if the element in the array is prime or not. If it prime, then its contribution is arr[i]2(N-1) times to the answer.
Below is the implementation of the above approach:

## C++

 `// C++ program to find the product of``// the multiplication of``// prime numbers in all possible subsets.``#include ``using` `namespace` `std;` `// Sieve method to check prime or not``void` `sieve(``int` `n, vector<``bool``>& prime)``{``    ``// Initially mark all primes``    ``for` `(``int` `i = 2; i <= n; i++)``        ``prime[i] = ``true``;``    ``prime = prime = ``false``;` `    ``// Iterate and mark all the``    ``// non primes as false``    ``for` `(``int` `i = 2; i <= n; i++) {``        ``if` `(prime[i]) {``            ``// Multiples of prime marked as false``            ``for` `(``int` `j = i * i; j <= n; j += i) {``                ``prime[j] = ``false``;``            ``}``        ``}``    ``}``}` `// Function to find the sum``// of sum of all the subset``int` `sumOfSubset(``int` `a[], ``int` `n)``{` `    ``// Get the maximum element``    ``int` `maxi = *max_element(a, a + n);` `    ``// Declare a sieve array``    ``vector<``bool``> prime(maxi + 1);` `    ``// Sieve function called``    ``sieve(maxi, prime);` `    ``// Number of times an element``    ``// contributes to the answer``    ``int` `times = ``pow``(2, n - 1);` `    ``int` `sum = 1;` `    ``// Iterate and check``    ``for` `(``int` `i = 0; i < n; i++) {``        ``// If prime``        ``if` `(prime[a[i]])``        ``sum = sum * (``pow``(a[i], times)); ``// Contribution``    ``}` `    ``return` `sum;``}` `// Driver Code``int` `main()``{``    ``int` `a[] = { 3, 7 };``    ``int` `n = ``sizeof``(a) / ``sizeof``(a);``    ``cout << sumOfSubset(a, n);``}`

## Java

 `// Java program to find the product of``// the multiplication of``// prime numbers in all possible subsets.``import` `java.util.*;` `class` `GFG``{` `// Sieve method to check prime or not``static` `void` `sieve(``int` `n, ``boolean` `[]prime)``{``    ``// Initially mark all primes``    ``for` `(``int` `i = ``2``; i <= n; i++)``        ``prime[i] = ``true``;``    ``prime[``0``] = prime[``1``] = ``false``;` `    ``// Iterate and mark all the``    ``// non primes as false``    ``for` `(``int` `i = ``2``; i <= n; i++)``    ``{``        ``if` `(prime[i])``        ``{``            ``// Multiples of prime marked as false``            ``for` `(``int` `j = i * i; j <= n; j += i)``            ``{``                ``prime[j] = ``false``;``            ``}``        ``}``    ``}``}` `// Function to find the sum``// of sum of all the subset``static` `int` `sumOfSubset(``int` `a[], ``int` `n)``{` `    ``// Get the maximum element``    ``int` `maxi = Arrays.stream(a).max().getAsInt();` `    ``// Declare a sieve array``    ``boolean` `[]prime = ``new` `boolean``[maxi + ``1``];` `    ``// Sieve function called``    ``sieve(maxi, prime);` `    ``// Number of times an element``    ``// contributes to the answer``    ``int` `times = (``int``) Math.pow(``2``, n - ``1``);` `    ``int` `sum = ``1``;` `    ``// Iterate and check``    ``for` `(``int` `i = ``0``; i < n; i++)``    ``{``        ``// If prime``        ``if` `(prime[a[i]])``        ``sum = (``int``) (sum * (Math.pow(a[i], times)));``    ``}` `    ``return` `sum;``}` `// Driver Code``public` `static` `void` `main(String[] args)``{``    ``int` `a[] = { ``3``, ``7` `};``    ``int` `n = a.length;``    ``System.out.println(sumOfSubset(a, n));``}``}` `// This code is contributed by Rajput-Ji`

## Python3

 `# Python3 program to find the product of``# the multiplication of``# prime numbers in all possible subsets.``prime ``=` `[``True` `for` `i ``in` `range``(``100``)]` `# Sieve method to check prime or not``def` `sieve(n, prime):``    ` `    ``# Initially mark all primes``    ``for` `i ``in` `range``(``1``, n ``+` `1``):``        ``prime[i] ``=` `True``    ``prime[``0``] ``=` `prime[``1``] ``=` `False` `    ``# Iterate and mark all the``    ``# non primes as false``    ``for` `i ``in` `range``(``2``, n ``+` `1``):``        ``if` `(prime[i]):``            ` `            ``# Multiples of prime marked as false``            ``for` `j ``in` `range``(``2` `*` `i, n ``+` `1``, i):``                ``prime[j] ``=` `False` `# Function to find the Sum``# of Sum of all the subset``def` `SumOfSubset(a, n):` `    ``# Get the maximum element``    ``maxi ``=` `max``(a)` `    ``# Declare a sieve array` `    ``# Sieve function called``    ``sieve(maxi, prime)` `    ``# Number of times an element``    ``# contributes to the answer``    ``times ``=` `pow``(``2``, n ``-` `1``)` `    ``Sum` `=` `1` `    ``# Iterate and check``    ``for` `i ``in` `range``(n):``        ` `        ``# If prime``        ``if` `(prime[a[i]]):``            ``Sum` `=` `Sum` `*` `(``pow``(a[i], times)) ``# Contribution` `    ``return` `Sum` `# Driver Code``a ``=` `[``3``, ``7``]``n ``=` `len``(a)``print``(SumOfSubset(a, n))` `# This code is contributed``# by Mohit Kumar`

## C#

 `// C# program to find the product of``// the multiplication of``// prime numbers in all possible subsets.``using` `System;``using` `System.Linq;` `class` `GFG``{` `// Sieve method to check prime or not``static` `void` `sieve(``int` `n, Boolean []prime)``{``    ``// Initially mark all primes``    ``for` `(``int` `i = 2; i <= n; i++)``        ``prime[i] = ``true``;``    ``prime = prime = ``false``;` `    ``// Iterate and mark all the``    ``// non primes as false``    ``for` `(``int` `i = 2; i <= n; i++)``    ``{``        ``if` `(prime[i])``        ``{``            ``// Multiples of prime marked as false``            ``for` `(``int` `j = i * i; j <= n; j += i)``            ``{``                ``prime[j] = ``false``;``            ``}``        ``}``    ``}``}` `// Function to find the sum``// of sum of all the subset``static` `int` `sumOfSubset(``int` `[]a, ``int` `n)``{` `    ``// Get the maximum element``    ``int` `maxi = a.Max();` `    ``// Declare a sieve array``    ``Boolean []prime = ``new` `Boolean[maxi + 1];` `    ``// Sieve function called``    ``sieve(maxi, prime);` `    ``// Number of times an element``    ``// contributes to the answer``    ``int` `times = (``int``) Math.Pow(2, n - 1);` `    ``int` `sum = 1;` `    ``// Iterate and check``    ``for` `(``int` `i = 0; i < n; i++)``    ``{``        ``// If prime``        ``if` `(prime[a[i]])``        ``sum = (``int``) (sum * (Math.Pow(a[i], times)));``    ``}``    ``return` `sum;``}` `// Driver Code``public` `static` `void` `Main(String[] args)``{``    ``int` `[]a = { 3, 7 };``    ``int` `n = a.Length;``    ``Console.WriteLine(sumOfSubset(a, n));``}``}` `// This code is contributed by PrinciRaj1992`

## Javascript

 ``
Output:

`441`

Time Complexity: O(M log M) for pre calculation where M is the maximum element and O(N) for iteration.
Space Complexity: O(M)
Note: As arr[i]2(N-1) can be really big, the answer can overflow, its preferable to use larger data-type and mod operations to conserve the answer.

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