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