By | 24.03.2017

# Multiplication by Russian peasant method

Write a C Program to perform Multiplication by Russian peasant method. Here’s simple Program to perform Multiplication by Russian peasant method using Recursion in C Programming Language.

## Recursion : :

• Recursion is the process of repeating items in a self-similar way. In programming languages, if a program allows you to call a function inside the same function, then it is called a recursive call of the function.
• The C programming language supports recursion, i.e., a function to call itself. But while using recursion, programmers need to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.
• Recursive functions are very useful to solve many mathematical problems, such as calculating the factorial of a number, generating Fibonacci series, etc.

## Russian peasant algorithm : :

One interesting method is the Russian peasant algorithm. The idea is to double the first number and halve the second number repeatedly till the second number doesn’t become 1.

In the process, whenever the second number become odd, we add the first number to result (result is initialized as 0)

Below is the source code for C Program to perform Multiplication by Russian peasant method using Recursion which is successfully compiled and run on Windows System to produce desired output as shown below :

### SOURCE CODE : :

```/* Multiplication by Russian peasant method*/

#include<stdio.h>
int f(int a, int b);
int main()
{
int a,b;
printf("Enter two numbers below ::\n ");
printf("\nEnter 1st number :: ");
scanf("%d",&a);
printf("\nEnter 2nd number :: ");
scanf("%d",&b);
printf("\nMultiplication of two numbers :: ");
printf("%d\n",f(a,b));

return 0;

}
int f(int a, int b)
{
if(a==0) /*if we write if(a==1) return b; then 0 * b can not be computed, so this condition*/
return 0;
if(a%2!=0)  /*if a is odd*/
return b + f(a/2, b*2);
return f(a/2, b*2);
}```

### OUTPUT  : :

```************* OUTPUT **************

************* FIRST RUN ***********

Enter two numbers below ::

Enter 1st number :: 4

Enter 2nd number :: 6

Multiplication of two numbers :: 24

************* SECOND RUN ***********

Enter two numbers below ::

Enter 1st number :: 6

Enter 2nd number :: 8

Multiplication of two numbers :: 48```

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Category: C Programming Recursion Programs Tags:  