Skip to content
Related Articles

Related Articles

Improve Article
Program to check Strong Number
  • Difficulty Level : Easy
  • Last Updated : 21 Apr, 2021

Strong Numbers are the numbers whose sum of factorial of digits is equal to the original number. Given a number, check if it is a Strong Number or not.
Examples: 
 

Input  : n = 145
Output : Yes
Sum of digit factorials = 1! + 4! + 5!
                        = 1 + 24 + 120
                        = 145

Input :  n = 534
Output : No

 

 

1) Initialize sum of factorials as 0. 
2) For every digit d, do following
   a) Add d! to sum of factorials.
3) If sum factorials is same as given 
   number, return true.
4) Else return false.

An optimization is to precompute factorials of all numbers from 0 to 10.
 

C++




// C++ program to check if a number is
// strong or not.
#include <bits/stdc++.h>
using namespace std;
 
int f[10];
 
// Fills factorials of digits from 0 to 9.
void preCompute()
{
    f[0] = f[1] = 1;
    for (int i = 2; i<10; ++i)
        f[i] = f[i-1] * i;
}
 
// Returns true if x is Strong
bool isStrong(int x)
{
    int factSum = 0;
 
    // Traverse through all digits of x.
    int temp = x;
    while (temp)
    {
        factSum += f[temp%10];
        temp /= 10;
    }
 
    return (factSum == x);
}
 
// Driver code
int main()
{
    preCompute();
 
    int x = 145;
    isStrong(x) ? cout << "Yes\n" : cout << "No\n";
    x = 534;
    isStrong(x) ? cout << "Yes\n" : cout << "No\n";
    return 0;
}       

Java




// Java program to check if
// a number is Strong or not
 
class CheckStrong
{
    static int f[] = new int[10];
  
    // Fills factorials of digits from 0 to 9.
    static void preCompute()
    {
        f[0] = f[1] = 1;
        for (int i = 2; i<10; ++i)
            f[i] = f[i-1] * i;
    }
     
    // Returns true if x is Strong
    static boolean isStrong(int x)
    {
        int factSum = 0;
      
        // Traverse through all digits of x.
        int temp = x;
        while (temp>0)
        {
            factSum += f[temp%10];
            temp /= 10;
        }
      
        return (factSum == x);
    }
     
    // main function
    public static void main (String[] args)
    {  
        // calling preCompute
        preCompute();
     
        // first pass
        int x = 145;
        if(isStrong(x))
        {
            System.out.println("Yes");
        }
        else
            System.out.println("No");
             
        // second pass
        x = 534;
        if(isStrong(x))
        {
            System.out.println("Yes");
        }
        else
            System.out.println("No");
    }
}

Python




# Python program to check if a number is
# strong or not.
 
f = [None] * 10
 
# Fills factorials of digits from 0 to 9.
def preCompute() :
    f[0] = f[1] = 1;
    for i in range(2,10) :
        f[i] = f[i-1] * i
  
# Returns true if x is Strong
def isStrong(x) :
     
    factSum = 0
    # Traverse through all digits of x.
    temp = x
    while (temp) :
        factSum = factSum + f[temp % 10]
        temp = temp / 10
 
    return (factSum == x)
     
# Driver code
preCompute()
x = 145
if(isStrong(x) ) :
    print "Yes"
else :
    print "No"
x = 534
if(isStrong(x)) :
    print "Yes"
else:
    print "No"
 
# This code is contributed by Nikita Tiwari.

C#




// C# program to check if
// a number is Strong or not
using System;
 
class CheckStrong
{
    static int []f = new int[10];
 
    // Fills factorials of digits from 0 to 9.
    static void preCompute()
    {
        f[0] = f[1] = 1;
        for (int i = 2; i < 10; ++i)
            f[i] = f[i - 1] * i;
    }
     
    // Returns true if x is Strong
    static bool isStrong(int x)
    {
        int factSum = 0;
     
        // Traverse through all digits of x.
        int temp = x;
        while (temp > 0)
        {
            factSum += f[temp % 10];
            temp /= 10;
        }
     
        return (factSum == x);
    }
     
    // Driver Code
    public static void Main ()
    {
        // calling preCompute
        preCompute();
     
        // first pass
        int x = 145;
        if(isStrong(x))
        {
            Console.WriteLine("Yes");
        }
        else
            Console.WriteLine("No");
             
        // second pass
        x = 534;
        if(isStrong(x))
        {
            Console.WriteLine("Yes");
        }
        else
            Console.WriteLine("No");
    }
}
 
// This code is contributed by Nitin Mittal.

PHP




<?php
// PHP program to check if a number
// is strong or not.
 
$f[10] = array();
 
// Fills factorials of digits
// from 0 to 9.
function preCompute()
{
    global $f;
    $f[0] = $f[1] = 1;
    for ($i = 2; $i < 10; ++$i)
        $f[$i] = $f[$i - 1] * $i;
}
 
// Returns true if x is Strong
function isStrong($x)
{
    global $f;
    $factSum = 0;
 
    // Traverse through all digits of x.
    $temp = $x;
    while ($temp)
    {
        $factSum += $f[$temp % 10];
        $temp = (int)$temp / 10;
    }
 
    return ($factSum == $x);
}
 
// Driver code
preCompute();
$x = 145;
 
if(isStrong(!$x))
    echo "Yes\n";
else
    echo "No\n";
$x = 534;
if(isStrong($x))
    echo "Yes\n";
else
    echo "No\n";
     
// This code is contributed by jit_t
?>

Javascript




<script>
 
// Javascript program to check if a number is
// strong or not.
 
 
let f = new Array(10);
 
// Fills factorials of digits from 0 to 9.
function preCompute()
{
    f[0] = f[1] = 1;
    for (let i = 2; i<10; ++i)
        f[i] = f[i-1] * i;
}
 
// Returns true if x is Strong
function isStrong(x)
{
    let factSum = 0;
 
    // Traverse through all digits of x.
    let temp = x;
    while (temp)
    {
        factSum += f[temp%10];
        temp = Math.floor(temp/10);
    }
 
    return (factSum == x);
}
 
// Driver code
 
    preCompute();
 
    let x = 145;
    isStrong(x) ? document.write("Yes" + "<br>") :
    document.write("No" + "<br>");
    x = 534;
    isStrong(x) ? document.write("Yes" + "<br>") :
    document.write("No" + "<br>");
 
 
//This code is contributed by Mayank Tyagi
 
</script>

Output: 

Yes
No

This article is contributed by Pramod Kumar. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 

Attention reader! Don’t stop learning now. Get hold of all the important mathematical concepts for competitive programming with the Essential Maths for CP Course at a student-friendly price. To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.




My Personal Notes arrow_drop_up
Recommended Articles
Page :