Write a C program to increment number without using + sign

 

#include <stdio.h>

int Increment(unsigned int i)
{
	unsigned int mask = 1;
	while (i & mask)		// Step 1
	{
		i = i & (~mask);	// Step 2
		mask = (mask<<1);	// Step 3
	}
	i = i | mask;			// Step 4
	
	return i;
}

int main( )
{
	printf("%d", Increment(1));
	
	return 0;
}

 

Explanation with example – Let we take example of number 1, so output would be 2 as we know, but we would go through each step separately so that logic become more clear.

Step 1: – Binary of ‘1’ is 0001 which will AND(&) with mask and result would be 1.

Step 2: – this step is simplified like this,

               i = i & (~mask);            // Step 2

               i = (0001) & (~0001);    

               i = (0001) & (1110);   

               i = 0

Step 3: – mast now shifted left, so it become 2,

Step 4: – Now value of i = 0, mask = 2

               So,    i = i | mask;            // Step 4

               i = 0000 | 00010;

               i = 2 , and here is output

Output

 

Suggested Reading

1. Add two numbers without using arithmetic operators
2. Smallest of three integers without comparison operators
3. Find middle number out of three numbers