PHP Program to Check Evil Number

Posted in PHP Tutorial

Updated on Jan 11, 2024

By Mari Selvan

👁️ 28 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the realm of programming, understanding the properties of numbers is a fascinating journey. One interesting concept is that of Evil Numbers.

An Evil Number is a non-negative integer that has an even number of '1' bits in its binary representation.

In this tutorial, we will explore a PHP program designed to check whether a given number is an Evil Number.

The program involves converting the decimal number to its binary representation and counting the number of '1' bits.

📄 Example

Let's delve into the PHP code that accomplishes this task.

isEvilNumber.php

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<?php
// Function to count the number of set bits (1s) in binary representation
function countSetBits($number)
{
  $count = 0;

  while ($number)
  {
    $count += $number & 1;
    $number >>= 1;
  }

  return $count;
}

// Function to check if a number is an Evil Number
function isEvilNumber($number)
{
  // Count the number of set bits in the binary representation
  $setBitsCount = countSetBits($number);

  // If the count of set bits is even, it is an Evil Number
  return $setBitsCount % 2 == 0;
}

// Driver program
// Replace this value with the number you want to check
$number = 15;

// Call the function to check if the number is an Evil Number
if (isEvilNumber($number)) echo "$number is an Evil Number.\n";
else echo "$number is not an Evil Number.\n";

?>

💻 Testing the Program

To test the program with different numbers, modify the value of $number in the code.

Output

15 is an Evil Number.

🧠 How the Program Works

The program defines a function countSetBits that takes an integer $number as input and returns the count of set bits (1s) in its binary representation.
The function isEvilNumber checks if the count of set bits is even, indicating that the number is an Evil Number.
Inside the main program, replace the value of $number with the desired number you want to check.
The program calls the isEvilNumber function and prints the result using echo.

📏 Between the Given Range

Let's explore the php code that checks for Evil Numbers in the specified range.

isEvil.php

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<?php
// Function to check if a number is evil
function isEvil($number)
{
  $binaryRepresentation = decbin($number);
  $countOnes = substr_count($binaryRepresentation, '1');
  return $countOnes % 2 == 0;
}

// Range for Evil Numbers
$lowerLimit = 1;
$upperLimit = 10;

// Display Evil Numbers in the range
echo "Evil numbers in the range $lowerLimit to $upperLimit: ";

for ($i = $lowerLimit;$i <= $upperLimit;$i++)
{
  if (isEvil($i))
  {
    echo "$i ";
  }
}

?>

💻 Testing the Program

The provided PHP program checks for Evil Numbers in the range from 1 to 10. To test with a different range, adjust the values of $lowerLimit and $upperLimit accordingly.

Output

Evil numbers in the range 1 to 10:
3 5 6 9 10

Run the script to see the Evil Numbers in the specified range.

🧠 How the Program Works

The program defines a function isEvil that takes a number as input, converts it to binary, and checks if it has an even number of 1s in its binary representation.
The range of numbers to be checked for Evil Numbers is set from 1 to 10.
The program iterates through each number in the range and prints the Evil Numbers.

🧐 Understanding the Concept of Evil Number

Before delving into the code, let's understand the concept of Evil Numbers. An Evil Number is a non-negative integer that has an even number of '1' bits in its binary representation.