Check whether a given number is even or odd

Given a number, check whether it is even or odd.

Examples :

Input: 2 
Output: even

Input: 5
Output: odd

One simple solution is to find the remainder after dividing by 2. 

Method 1:

C++

// A simple C++ program to
// check for even or odd
#include <iostream>
using namespace std;

// Returns true if n is
// even, else odd
bool isEven(int n) { return (n % 2 == 0); }

// Driver code
int main()
{
    int n = 101;
    isEven(n) ? cout << "Even" : cout << "Odd";

    return 0;
}

Java

// Java program  to
// check for even or odd

class GFG {
    // Returns true if n is even, else odd
    public static boolean isEven(int n)
    {
        return (n % 2 == 0);
    }

    // Driver code
    public static void main(String[] args)
    {
        int n = 101;
        if (isEven(n) == true)
            System.out.print("Even");
        else
            System.out.print("Odd");
    }
}

// This code is contributed by rishabh_jain

Python3

# A simple Python3 code
# to check for even or odd

# Returns true if n is even, else odd


def isEven(n):
    return (n % 2 == 0)


# Driver code
n = 101
print("Even" if isEven(n) else "Odd")

# This code is contributed by "Sharad_Bhardwaj".

C#

// C# program to
// check for even or odd
using System;

class GFG {
    // Returns true if n is even, else odd
    public static bool isEven(int n)
    {
        return (n % 2 == 0);
    }

    // Driver code
    public static void Main()
    {
        int n = 101;
        if (isEven(n) == true)
            Console.WriteLine("Even");
        else
            Console.WriteLine("Odd");
    }
}

// This code is contributed by vt_m

PHP

<?php
// A simple PHP program to
// check for even or odd

// Returns true if n is
// even, else odd
function isEven($n)
{
    return ($n % 2 == 0);
}

// Driver code
$n = 101;
if(isEven($n) == true)
    echo "Even";
    else
    echo "Odd";

// This code is contributed by Ajit
?>

Javascript

<script>

// A simple Javascript program to
// check for even or odd


// Returns true if n is
// even, else odd
function isEven(n) { return (n % 2 == 0); }

// Driver code

    let n = 101;
    isEven(n) ? document.write("Even") :document.write("Odd");


// This code is contributed by Mayank Tyagi

</script>

Output

Odd

Time Complexity: O(1)
Auxiliary Space: O(1)

Method 2 :

A better solution is to use bitwise operators. We need to check whether the last bit is 1 or not. If the last bit is 1 then the number is odd, otherwise always even.

Explanation: 

 input : 5    // odd
   00000101              
 & 00000001                
--------------                
   00000001       
--------------

input : 8     //even
   00001000              
 & 00000001                 
--------------               
   00000000        
--------------

Below is the implementation of the idea. 

C++

// A simple C++ program to
// check for even or odd
#include <iostream>
using namespace std;

// Returns true if n is
// even, else odd
bool isEven(int n)
{

    // n & 1 is 1, then
    // odd, else even
    return (!(n & 1));
}

// Driver code
int main()
{
    int n = 101;
    isEven(n) ? cout << "Even" : cout << "Odd";

    return 0;
}

C

#include <math.h>
#include <stdio.h>

int main()
{
    int n = 101;
    if (n % 2 == 0) {
        printf("Even");
    }
    else {
        printf("Odd");
    }
    return 0;
}

Java

// Java program to
// check for even or odd

class GFG {
    // Returns true if n
    // is even, else odd
    public static boolean isEven(int n)
    {
        if ((n & 1) == 0)
            return true;
        else
            return false;
    }

    // Driver code
    public static void main(String[] args)
    {
        int n = 101;
        if (isEven(n) == true)
            System.out.print("Even");
        else
            System.out.print("Odd");
    }
}

// This code is contributed by rishabh_jain

Python3

# A Python3 code program
# to check for even or odd

# Returns true if n is even, else odd


def isEven(n):

    # n&1 is 1, then odd, else even
    return (not(n & 1))


# Driver code
n = 101
print("Even" if isEven(n) else "Odd")

# This code is contributed by "Sharad_Bhardwaj".

C#

// C# program  to
// check for even or odd
using System;

class GFG {
    // Returns true if n
    // is even, else odd
    public static bool isEven(int n)
    {
        if ((n & 1) == 0)
            return true;
        else
            return false;
    }

    // Driver code
    public static void Main()
    {
        int n = 101;
        if (isEven(n) == true)
            Console.WriteLine("Even");
        else
            Console.WriteLine("Odd");
    }
}

// This code is contributed by vt_m.

PHP

<?php
// A simple PHP program to
// check for even or odd

// Returns true if n is
// even, else odd
function isEven($n)
{
    return (!($n & 1));
}

// Driver code
$n = 101;
if(isEven($n) == true)
    echo "Even";
else
    echo "Odd";

// This code is contributed by Smitha
?>

Javascript

<script>
// A simple JavaScript program to
// check for even or odd

// Returns true if n is
// even, else odd
function isEven(n)
{

    // n & 1 is 1, then
    // odd, else even
    return (!(n & 1));
}

// Driver code
let n = 101;
isEven(n)? document.write("Even") :
        document.write("Odd");

// This code is contributed by Manoj.
</script>

Output

Odd

Time Complexity: O(1)
Auxiliary Space: O(1)

Method 3: Another approach is by using bitwise left-shift and right-shift operators. The logic behind this implementation is about regenerating the value after the right shift and left shift. We all know even numbers have zero as the last bit and odd have one as the last bit. When we bitwise right shift any number then the last bit of the number piped out whenever it is even or odd. Next, we did a bitwise left shift, then our bit shifted by one. Now last bit placed is empty which is by default filled by a zero. During all these odd numbers changed their value but even remains the same. That’s how by comparing the initial and final value we decide number is even or odd.

below is the implementation of the above logic.

C++

#include <bits/stdc++.h>
using namespace std;

int main()
{

    int a = 4;
    // To take input from user, prefer below code
    // int a ;
    // cout<<"Enter an number: " <<"\n";
    // cin>>a;

    if (a == (a >> 1) << 1) {
        cout << "Number is Even: " << a << endl;
    }
    else {
        cout << "Number is Odd: " << a << endl;
    }

    // below is short hand
    // a==(a>>1)<<1? printf("Number %d is
    // even.\n",a):printf("Number %d is odd.\n",a);

    return 0;
}

Java

// Java implementation of above approach
import java.io.*;
class HelloWorld {
    public static void main(String[] args)
    {
        int a = 4;

        // To take input from user, prefer below code
        // int a ;
        // printf("Enter an number: \n");
        // scanf("%d",&a);
        if (a == (a >> 1) << 1) {
            System.out.printf("Number %d is even.\n", a);
        }
        else {
            System.out.printf("Number %d is not even.\n",
                              a);
        }

        // below is short hand
        // a==(a>>1)<<1? printf("Number %d is
        // even.\n",a):printf("Number %d is odd.\n",a);
    }
}

// This code is contributed by karandeep1234.

Python3

a = 4
if a == (a >> 1) << 1:
    print("Number is Even:", a)
else:
    print("Number is Odd:", a)

C#

// C# implementation of above approach
using System;

class HelloWorld {
    public static void Main(string[] args)
    {
        int a = 4;

        if (a == (a >> 1) << 1) {
            Console.WriteLine("Number " + a + " is even.");
        }
        else {
            Console.WriteLine("Number " + a
                              + " is not even.");
        }

        // below is short hand
        // a==(a>>1)<<1? printf("Number %d is
        // even.\n",a):printf("Number %d is odd.\n",a);
    }
}

// This code is contributed by karandeep1234.

Javascript

const a = 4;

// To take input from user, prefer below code
// let a = prompt("Enter a number: ");

// Check if the number is even
if (a == (a >> 1) << 1) {
    console.log("Number is Even: " + a);
}
else {
    console.log("Number is Odd: " + a);
}

// This code is contributed by Shivam Tiwari

Output

Number 4 is even.
Number is Even: 4

Time Complexity: O(1)
Auxiliary Space: O(1)

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