Check Strong Number

Check Strong Number in C++ (5 Programs)

IntermediateTopic: Advanced Number Programs
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C++ Check Strong Number Program

This program helps you to learn the fundamental structure and syntax of C++ programming.

Try This Code
#include <iostream>
using namespace std;

int factorial(int n) {
    if (n == 0 || n == 1) return 1;
    return n * factorial(n - 1);
}

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

int main() {
    int num;
    cout << "Enter a number: ";
    cin >> num;
    
    if (isStrong(num)) {
        cout << num << " is a Strong number" << endl;
    } else {
        cout << num << " is not a Strong number" << endl;
    }
    
    return 0;
}
Output
Enter a number: 145
145 is a Strong number

Understanding Check Strong Number

A Strong number is a number where the sum of factorials of its digits equals the number itself. For example, 145 = 1! + 4! + 5! = 1 + 24 + 120 = 145. This program demonstrates 5 different methods to check for strong numbers.

Note: To write and run C++ programs, you need to set up the local environment on your computer. Refer to the complete article Setting up C++ Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your C++ programs.

Practical Learning Notes for Check Strong Number

This C++ program is part of the "Advanced Number Programs" topic and is designed to help you build real problem-solving confidence, not just memorize syntax. Start by understanding the goal of the program in plain language, then trace the logic line by line with a custom input of your own. Once you can predict the output before running the code, your understanding becomes much stronger.

A reliable practice pattern is to run the original version first, then modify only one condition or variable at a time. Observe how that single change affects control flow and output. This deliberate style helps you understand loops, conditions, and data movement much faster than copying full solutions repeatedly.

For interview preparation, explain this solution in three layers: the high-level approach, the step-by-step execution, and the time-space tradeoff. If you can teach these three layers clearly, you are ready to solve close variations of this problem under time pressure.

Next
Calculate Power of a Number
Next
Calculate Power of a Number

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