Strong Number in C, C++, Java & Python – Code with Explanation & Examples in Short and Simple

   

C Program

/* C - check Strong Number (input: 145) */
#include <stdio.h>

int main() {
    int n, t, sum = 0;
    int fact[10] = {1,1,2,6,24,120,720,5040,40320,362880};
    if (scanf("%d", &n)!=1) return 0;
    t = n;
    while (t > 0) {
        sum += fact[t % 10];
        t /= 10;
    }
    if (sum == n) printf("%d is a Strong Number\n", n);
    else printf("%d is NOT a Strong Number\n", n);
    return 0;
}

C Output

Input:
145
Output:
145 is a Strong Number

C++ Program

// C++ - check Strong Number (input: 5)
#include <iostream>
using namespace std;
int main() {
    int n; if (!(cin >> n)) return 0;
    int f[10] = {1,1,2,6,24,120,720,5040,40320,362880};
    int t = n, s = 0;
    while (t) { s += f[t % 10]; t /= 10; }
    cout << n << (s == n ? " is a Strong Number\n" : " is NOT a Strong Number\n");
    return 0;
}

C++ Output

Input:
5
Output:
5 is NOT a Strong Number

JAVA Program

// Java - check Strong Number (input: 1)
import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        if (!sc.hasNextInt()) return;
        int n = sc.nextInt();
        int[] f = {1,1,2,6,24,120,720,5040,40320,362880};
        int t = n, sum = 0;
        while (t > 0) { sum += f[t % 10]; t /= 10; }
        System.out.println(n + (sum == n ? " is a Strong Number" : " is NOT a Strong Number"));
    }
}

JAVA Output

Input:
1
Output:
1 is a Strong Number

Python Program

# Python - check Strong Number (input: 40585)
import sys
n = int(sys.stdin.read().strip() or 0)
f = [1,1,2,6,24,120,720,5040,40320,362880]
t, s = n, 0
while t:
    s += f[t % 10]
    t //= 10
print(f"{n} is a Strong Number" if s == n else f"{n} is NOT a Strong Number")

Python Output

Input:
40585
Output:
40585 is a Strong Number

In-Depth Learning – Entire Concept in Paragraphs

Example: A Strong Number is a number which is equal to the sum of the factorials of its digits. 145 is strong, for example, since 1! + 4! + 5! = 145 exactly. The above code reads an integer, splits it into its digits by repeatedly applying modulus and division, looks up the factorial of each digit in a small lookup table (0! to 9!) and totals them together. After calculating all the digits, it checks the sum accumulated so far with the original number and prints whether the number is strong or not. A precomputed factorial table prevents repeated extensive calculations and makes the program concise and efficient.

Real-Life Analogy: 

Consider every digit as a small worker that makes a constant number of widgets equal to its factorial. The original number is similar to an order quantity. If all the digit-workers together produce exactly enough widgets to meet the original order, then the number "fulfills" its requirement — it's autonomous, the way a Strong Number is when it equals the sum of the digits' contributions to factorial. This connection makes the concept feel concrete: digits create a known output and the sum is measured against the initial demand.

Why It Matters: 

This exercise is a small illustration of breaking down problems into simpler pieces and applying lookup optimization. It illustrates how to get the digits out, how not to do repeated computation with memoization (a small fixed memo for factorials), and how to use numeric properties in reasoning. These concepts generalize: digit manipulation shows up in checksum routines, encoding operations, and validation checks throughout software systems.

Learning Insights:

 Performing Strong Number checks enforces a number of fundamental programming skills. You drill reading input robustly in a variety of languages, working with loops and integer arithmetic correctly, and structuring small helper data (the factorial array). The theme of "reduce a number to its digits and aggregate a function over them" applies to a great variety of useful tasks such as calculating digit sums, testing Armstrong numbers, or generating checksums. Employing constant-time lookup (the precomputed factorial table) illustrates how a modest memory exchange can greatly reduce and accelerate computation when inputs consist of recurrent small-domain calculations.

Interview Usage Examples: 

Interviewers prefer this problem because it tests fundamental coding proficiency without concealing complexity. It allows you to demonstrate clean digit picking, easy optimizations, and concise output formatting. You can prolong the conversation during an interview by discussing performance, edge cases (single-digit and zero numbers), or how you would modify the approach to very large numbers (potentially using strings and big-integer libraries). The candidate who speaks of precomputation of factorials, and addresses input checking and big values in a few words, indicates practical and theoretical insight.

Real-World Application: 

Strong Numbers themselves are largely a curiosity, but the method is important in real-world projects. Digit-by-digit processing is applied in verification algorithms such as credit card number validation with Luhn's algorithm, identifier parsing, and lightweight cryptographic checksums. The concept of mapping a small range (0–9) to precomputed values is a typical micro-optimization employed in parsers, codecs, and embedded applications where CPU cycles are invaluable but a few bytes for a lookup table are fine.

Why This Implementation: 

The implementations selected are deliberately terse and resilient. Precomputing factorials makes loops minuscule and sidesteps function call overhead. Applying integer arithmetic to extract digits is more efficient than string conversion when numbers can fit in native types. All the language samples read a single int and output a human-readable judgment so beginners can execute and test immediately. The Python sample takes piped input or standard input, following typical beginner patterns, and the compiled languages take simple scanf/cin/Scanner patterns.

Edge Cases and Notes: 

One-digit numbers 1 and 2 are Strong because 1! = 1 and 2! = 2. Zero (0) can traditionally be considered not strong because 0! = 1 and 0 ! = 1, although implementations may determine behavior for nonpositive arguments explicitly.

Large Strong Numbers are uncommon; aside from 1 and 2, the famous Strong Numbers in base 10 are 145 and 40585. Having these allows you to test correctness in more than trivial cases. SEO-friendly explanation paragraph: A Strong Number test is a simple-to-run coding practice to practice digit extraction, lookup optimization, and fundamental control structures in C, C++, Java, and Python. This Strong Number illustration illustrates how to calculate factorials for digits efficiently using a precomputed table and illustrates straightforward input/output patterns learners must practice for practice questions and interview questions. Beginners looking for "Strong Number program", "check strong number in C C++ Java Python", or "digit factorial sum equals number example" will be able to see these brief, functioning implementations and the detailed rationale useful for learning equivalent numeric problems and applying the concepts in real-world verification or coding-interview settings.