Russian Peasant Multiplication | GeeksforGeeks

Given two integers, write a function to multiply them without using multiplication operator.
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)

Let the two given numbers be 'a' and 'b'
1) Initialize result 'res' as 0.
2) Do following while 'b' is greater than 0
   a) If 'b' is odd, add 'a' to 'res'
   b) Double 'a' and halve 'b'
3) Return 'res'. 

unsigned int russianPeasant(unsigned int a, unsigned int b)

{

    int res = 0;  // initialize result

 

    // While second number doesn't become 1

    while (b > 0)

    {

         // If second number becomes odd, add the first number to result

         if (b & 1)

             res = res + a;

 

         // Double the first number and halve the second number

         a = a << 1;

         b = b >> 1;

     }

     return res;

}

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