using System;
/*
Example: 57 * 18
57 18
Halving the first column:
28 18
14
7
3
1
Doubling the second column:
28 36
14 72
7 144
3 288
1 576
Remove rows whose first cell is even:
18
28 36 x
14 72 x
7 144
3 288
1 576
Sum the remaining numbers in the right-hand column:
18
28 -
14 -
7 162
3 288
1 576
====
1026
*/
class Program
{
static int EthiopianMultiply(int a, int b)
{
int sum = 0;
while (a > 0)
{
if (a % 2 == 1) // keep only odd rows
{
sum += b;
Console.WriteLine("sum = " + sum);
}
a /= 2; // halve left side
b *= 2; // double right side
Console.WriteLine("a = " + a + " b = " + b);
}
return sum;
}
static void Main()
{
int a = 57;
int b = 18;
Console.WriteLine(EthiopianMultiply(a, b));
}
}
/*
run:
sum = 18
a = 28 b = 36
a = 14 b = 72
a = 7 b = 144
sum = 162
a = 3 b = 288
sum = 450
a = 1 b = 576
sum = 1026
a = 0 b = 1152
1026
*/
