C++ Program to Check Strong Number

Posted in C++ Tutorial

Updated on Oct 06, 2024

By Mari Selvan

👁️ 87 - Views

⏳ 4 mins

💬 1 Comment

Photo Credit to CodeToFun

🙋 Introduction

In the world of programming, exploring number properties is a fascinating journey. One such property is related to Strong Numbers.

A Strong Number (also known as a Digital Factorial) is a number in which the sum of the factorials of its digits is equal to the number itself.

In this tutorial, we'll delve into a C++ program that checks whether a given number is a Strong Number or not.

📄 Example

Let's take a look at the C++ code that checks whether a given number is a Strong Number.

isStrongNumber.c

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#include <iostream>

// Function to calculate the factorial of a number
int factorial(int num) {
  if (num == 0 || num == 1) {
    return 1;
  } else {
    return num * factorial(num - 1);
  }
}

// Function to check if a number is a Strong Number
bool isStrongNumber(int num) {
  int originalNum = num;
  int sum = 0;

  while (num > 0) {
    int digit = num % 10;
    sum += factorial(digit);
    num /= 10;
  }

  return (sum == originalNum);
}

// Driver program
int main() {
  // Replace this value with your desired number
  int number = 145;

  // Call the function to check if the number is a Strong Number
  if (isStrongNumber(number)) {
    std::cout << number << " is a Strong Number." << std::endl;
  } else {
    std::cout << number << " is not a Strong Number." << std::endl;
  }

  return 0;
}

💻 Testing the Program

To test the program with different numbers, simply replace the value of number in the main function.

Output

145 is a Strong Number.

Compile and run the program to check if the number is a Strong Number.

🧠 How the Program Works

The program defines a function factorial to calculate the factorial of a number.
Another function isStrongNumber is defined to check if a given number is a Strong Number.
Inside the isStrongNumber function, it iterates through each digit of the number, calculates the factorial, and adds it to the sum.
The result is compared with the original number to determine if it is a Strong Number.

📏 Between the Given Range

Let's take a look at the C++ code that checks for strong numbers in the range of 1 to 200.

isStrong.cpp

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#include <iostream>

using namespace std;

// Function to calculate the factorial of a number
int factorial(int n) {
  if (n == 0 || n == 1) {
    return 1;
  } else {
    return n * factorial(n - 1);
  }
}

// Function to check if a number is strong
bool isStrong(int num) {
  int originalNum = num;
  int sum = 0;

  while (num > 0) {
    int digit = num % 10;
    sum += factorial(digit);
    num /= 10;
  }

  return (sum == originalNum);
}

// Driver program
int main() {
  cout << "Strong Numbers in the Range 1 to 200:" << endl;

  for (int i = 1; i <= 200; ++i) {
    if (isStrong(i)) {
      cout << i << " ";
    }
  }

  cout << endl;

  return 0;
}

💻 Testing the Program

Output

Strong Numbers in the Range 1 to 200:
1 2 145

Run the program to see the strong numbers in the range of 1 to 200.

🧠 How the Program Works

The program defines a function factorial to calculate the factorial of a number.
It also defines a function isStrong to check if a given number is a strong number.
The main function iterates through numbers in the range 1 to 200 and prints the strong numbers.

🧐 Understanding the Concept of Strong Number

To determine if a number is a Strong Number, we need to calculate the factorial of each digit of the number and then sum these factorials. If the sum is equal to the original number, then it is a Strong Number.

For example, let's consider the number 145:

The factorial of 1 is 1.
The factorial of 4 is 24.
The factorial of 5 is 120.

The sum of these factorials is 1 + 24 + 120 = 145, which is the original number. Hence, 145 is a Strong Number.

🎉 Conclusion

Understanding and implementing programs that check for mathematical properties, such as Strong Numbers, enhances problem-solving skills in programming. Feel free to modify and expand upon this code for your specific needs. Happy coding!