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Switch Sign of a Number

We make use of bit manipulation to solve this problem. using a NOT operator.

Gopi Gorantala
Gopi Gorantala
1 min read

Table of Contents

In this coding question, we use the NOT operator to switch the sign of a number.

Problem Statement

We need to write a program to switch the sign of a number.

Input: 10
Output: -10


We already know that 2’s complement of any number gives a negative number with the formula below.


~x = (232 - x)

For example,

>if, x = 1
    ~x = -2

 if, y = 10
    ~y = -11

So if you see the pattern, the number is negated and converted to 2’s complement.

    number  = 8
   ~number  = -9
~number + 1 = (-9 + 1) = -8



class SignChange {
    static int switchSign(int number){
      return ~number + 1;

    public static void main( String args[] ) {
      int number = 8;


def switchSign(number):
      return ~number + 1

number = 8


const switchSign = number => {
  return ~number + 1;

let number = 8;


#include <iostream>

using namespace std;

int main() {
    int number = 8;
    cout << (~number + 1);
    return 0;


export const switchSign = (n: number): number => {
    return (~n + 1);

let n: number = 8;

Complexity Analysis

Time Complexity

We are not running a loop or scaling the inputs. The inputs never change. So the operation takes a single unit of time, which is O(1).

Space Complexity

We didn’t create an extra memory for this. So, the space complexity is O(1).

Coding Interview QuestionsData Structures and AlgorithmsBit Manipulation

Gopi Gorantala Twitter

Gopi is an engineering leader with 12+ of experience in full-stack development—a specialist in Java technology stack. He worked for multiple startups, the European govt, and FAANG in India and Europe.


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