C# Program to Check Evil Number

Posted in C# Tutorial

Updated on Jan 11, 2024

By Mari Selvan

👁️ 25 - 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 delve into a C# 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 dive into the C# code that accomplishes this task.

Program.cs

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using System;

class Program {
  // Function to count the number of set bits (1s) in binary representation
  static int CountSetBits(int number) {
    int count = 0;

    while (number != 0) {
      count += number & 1;
      number >>= 1;
    }

    return count;
  }

  // Function to check if a number is an Evil Number
  static bool IsEvilNumber(int number) {
    // Count the number of set bits in the binary representation
    int setBitsCount = CountSetBits(number);

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

  // Driver program
  static void Main() {
    // Replace this value with the number you want to check
    int number = 15;

    // Call the function to check if the number is an Evil Number
    if (IsEvilNumber(number))
      Console.WriteLine($"{number} is an Evil Number.");
    else
      Console.WriteLine($"{number} is not an Evil Number.");
  }
}

💻 Testing the Program

To test the program with different numbers, modify the value of number in the Main method.

Output

15 is an Evil Number.

Run the script to check if the specified number is an Evil Number.

🧠 How the Program Works

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

📏 Between the Given Range

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

Program.cs

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using System;

class Program {
  // Function to check if a number is Evil
  static bool IsEvil(int num) {
    // Convert the number to binary
    string binaryRepresentation = Convert.ToString(num, 2);

    // Count the number of 1s in the binary representation
    int countOnes = 0;
    foreach(char digit in binaryRepresentation) {
      if (digit == '1')
        countOnes++;
    }

    // Check if the count of 1s is even
    return countOnes % 2 == 0;
  }

  // Driver program
  static void Main() {
    Console.WriteLine("Evil numbers in the range 1 to 10:");

    // Check numbers from 1 to 10 for Evilness
    for (int i = 1; i <= 10; i++) {
      if (IsEvil(i)) {
        Console.Write(i + " ");
      }
    }

    Console.WriteLine();
  }
}

💻 Testing the Program

Output

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

Run the program 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 and checks if it is an Evil Number.
Inside the function, it converts the number to its binary representation and counts the number of 1s.
The main function tests the Evilness for numbers in the range from 1 to 10 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.