Subtract 1 without arithmetic operators Java

Software Development
#1

Write a program to subtract one from a given number. The use of operators like ‘+’, ‘-‘, ‘*’, ‘/’, ‘++’, ‘–‘ …etc are not allowed.

Examples:

Input: 12 Output: 11 Input: 6 Output: 5

Method 1
To subtract 1 from a number x (say 0011001000), flip all the bits after the rightmost 1 bit (we get 0011001111). Finally, flip the rightmost 1 bit also (we get 0011000111) to get the answer.

  • Java

// Java code to subtract

// one from a given number

import java.io.*;

class GFG

{

static int subtractOne( int x)

{

int m = 1 ;

// Flip all the set bits

// until we find a 1

while (!((x & m) > 0 ))

{

x = x ^ m;

m <<= 1 ;

}

// flip the rightmost

// 1 bit

x = x ^ m;

return x;

}

// Driver Code

public static void main (String[] args)

{

System.out.println(subtractOne( 13 ));

}

}

Output:

12