Subtract two numbers using bit manipulation

Subtracting numbers is done similar to add number(refer previous post in this blog) with minor difference. Instead of direct and between x and y . We take negation of x to and.

	#include<stdio.h>
	int subtract(int x, int y)
	{
	// Iterate till there is no carry
	while (y != 0)
	{
	// borrow contains common set bits of y and unset
	// bits of x
	int borrow = (~x) & y;
	// Subtraction of bits of x and y where at least
	// one of the bits is not set
	x = x ^ y;
	// Borrow is shifted by one so that subtracting it from
	// x gives the required sum
	y = borrow << 1;
	}
	return x;
	}
	// Driver program
	int main()
	{
	int x = 29, y = 13;
	printf("x - y is %d", subtract(x, y));
	return 0;
	}

view raw subtractnumbers.c hosted with ❤ by GitHub