Find the Number of Maximum Product Quadruples in C++

Suppose we have one integer array with n elements. We have to find the maximum product of a quadruple in the array. So if the array is like [3, 5, 20, 6, 10], then final product is 6000, and elements in quadruple is 10, 5, 6, 20

To solve this, we will follow these steps −

• Sort the array in ascending order
• Suppose x be the product of last four elements, y be the product of first four elements, and z be the product of first two and second two elements
• Return the max of x, y and z.

Example

#include<iostream>
#include<algorithm>
using namespace std;
int maxQuadProduct(int arr[], int n) {
   if (n < 4)
   return -1;
   sort(arr, arr + n);
   int last_four = arr[n - 1] * arr[n - 2] * arr[n - 3] * arr[n - 4];
   int first_four = arr[0] * arr[1] * arr[2] * arr[3];
   int two_first_last = arr[0] * arr[1] * arr[n - 1] * arr[n - 2];
   return max(last_four, max(first_four, two_first_last));
}
int main() {
   int arr[] = { -10, -3, 5, 6, -20 };
   int n = sizeof(arr) / sizeof(arr[0]);
   int maximum_val = maxQuadProduct(arr, n);
   if (maximum_val == -1)
      cout << "No Quadruple Exists";
   else
      cout << "Maximum product is " << maximum_val;
}

Output

Maximum product is 6000