Swap 2 Number Without Temp Variable Using Bit Manipulation

Swapping 2 numbers without using any temporary variable can be done using arithmetic operations as well, but the algorithm is error-prone. The arithmetic approach will overflow if we try to add Integer.MAX_VALUE to Integer.MAX_VALUE.

Bit manipulation technique is the fast and most suitable way to swap 2 numbers.

package org.wesome.dsalgo;

import lombok.AllArgsConstructor;
import lombok.Data;

public class SwapTwoNumber {
    public static TwoNumbers swapTwoNumber(TwoNumbers twoNumbers) {
        System.out.println("a = " + twoNumbers.a + " b = " + twoNumbers.b);
        twoNumbers.a = twoNumbers.a ^ twoNumbers.b;
        twoNumbers.b = twoNumbers.a ^ twoNumbers.b;
        twoNumbers.a = twoNumbers.a ^ twoNumbers.b;
        System.out.println("a = " + twoNumbers.a + " b = " + twoNumbers.b);
        return twoNumbers;
    }

    @Data
    @AllArgsConstructor
    static class TwoNumbers {
        int a;
        int b;
    }
}

package org.wesome.dsalgo;

import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.assertAll;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class SwapTwoNumberTest {
    @Test
    void swapTwoNumberTest1() {
        SwapTwoNumber.TwoNumbers twoNumbers = new SwapTwoNumber.TwoNumbers(1, 2);
        SwapTwoNumber.TwoNumbers result = SwapTwoNumber.swapTwoNumber(twoNumbers);
        assertAll(() -> assertEquals(2, result.a), () -> assertEquals(1, result.b));
    }

    @Test
    void swapTwoNumberTest2() {
        SwapTwoNumber.TwoNumbers twoNumbers = new SwapTwoNumber.TwoNumbers(Integer.MIN_VALUE, Integer.MIN_VALUE);
        SwapTwoNumber.TwoNumbers result = SwapTwoNumber.swapTwoNumber(twoNumbers);
        assertAll(() -> assertEquals(Integer.MIN_VALUE, result.a), () -> assertEquals(Integer.MIN_VALUE, result.b));
    }

    @Test
    void swapTwoNumberTest3() {
        SwapTwoNumber.TwoNumbers twoNumbers = new SwapTwoNumber.TwoNumbers(Integer.MAX_VALUE, Integer.MAX_VALUE);
        SwapTwoNumber.TwoNumbers result = SwapTwoNumber.swapTwoNumber(twoNumbers);
        assertAll(() -> assertEquals(Integer.MAX_VALUE, result.a), () -> assertEquals(Integer.MAX_VALUE, result.b));
    }

    @Test
    void swapTwoNumberTest4() {
        SwapTwoNumber.TwoNumbers twoNumbers = new SwapTwoNumber.TwoNumbers(Integer.MAX_VALUE, Integer.MIN_VALUE);
        SwapTwoNumber.TwoNumbers result = SwapTwoNumber.swapTwoNumber(twoNumbers);
        assertAll(() -> assertEquals(Integer.MIN_VALUE, result.a), () -> assertEquals(Integer.MAX_VALUE, result.b));
    }

}

plugins {
    id 'java'
    id "io.freefair.lombok" version "6.2.0"
}

group = 'org.wesome'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = JavaVersion.VERSION_1_8

configurations {
    compileOnly {
        extendsFrom annotationProcessor
    }
}

repositories {
    mavenCentral()
}

dependencies {
    testImplementation 'org.junit.jupiter:junit-jupiter:5.6.2'
}

test {
    useJUnitPlatform()
}