## Tuesday, 1 March 2016

### Increment a number by one without using addition operator

Write a program to increment a number by one without using operators like ‘+’, ‘-‘, ‘*’, ‘/’, ‘++’, ‘–‘ …etc.

Examples:
Input: 20
Output: 21

We can achieve the functionality using bitwise operators.

Approach#
To increment the bit, we need to add 1 in binary representation. However addition is not allowed.
So we can check the each bit and flip it using bitwise operators.

Step#1 Flip all the set bits until we find a 0. (Alternate to Carry forward in addition)
Step#2 Flip the rightmost 0 bit (Add the new value at right side).

Bitwise representation of 20 is 10100.

public class IncrementByOne {
public static void main(String[] args) {
int value = 20;
value = increment(20);
System.out.println(value);
}

static int increment(int number) {
int one = 1;

/* Flip all the set bits until we find a 0 */
while((number & one)!=0 ) {
number = number^one;
one <<= 1;
}

/* flip the rightmost 0 bit */
number = number^one;
return number;
}
}
Output:
21