Question

Implement and complement the recursive code to compute the product of two positive integers, x and y, using only addition and/or subtraction. The function will take as its arguments two integers to multiply together ( x x y ) and will return the product.

Hint: consider the following:

6 x 1 = 6
6 x 2 = 6 + (6 x 1)
6 x 3 = 6 + (6 x 2) = 6 + [6 + (6 x 1)] = 6 + 6 + 6

#include<iostream>
using namespace std;

// Implement this product recursive function.

int product(int x, int y)
{

}

int main()
{
int x = 40, y = 10;
cout << "product(" << x << ", " << y << ")=";
cout << product(x, y) << endl;
return 0;
}

Answer 1

#include <bits/stdc++.h>
using namespace std;

// recursive function to calculate
// multiplication of two numbers
int product(int x, int y)
{
   // if x is less than
   // y swap the numbers
   if (x < y)
       return product(y, x);

   // iteratively calculate
   // y times sum of x
   else if (y != 0)
       return (x + product(x, y - 1));

   // if any of the two numbers is
   // zero return zero
   else
       return 0;
}

// Driver Code
int main()
{
   int x = 5, y = 2;
   cout << product(x, y);
   return 0;
}
----------------------------------------------------------------------------------------------------------------------------------------------------
#include<iostream>

using namespace std;
class GFG
{
  
/* function to multiply two numbers x and y*/
public : int multiply(int x, int y)
{
   /* 0 multiplied with anything gives 0 */
   if(y == 0)
   return 0;

   /* Add x one by one */
   if(y > 0 )
   return (x + multiply(x, y-1));

   /* the case where y is negative */
   if(y < 0 )
   return -multiply(x, -y);
}
};

// Driver code
int main()
{
   GFG g;
   cout << endl << g.multiply(5, -11);
   getchar();
   return 0;
}