Program to find Strong Numbers in a Given Range in Java

April 1, 2022

Strong Number in a Given Range in Java

Here, in this page we will discuss the program to find Strong Number in a Given Range in Java. We are given with two values and need to print the strong numbers between the given range.

Strong Number Strong number is a special number whose sum of the factorial of digits is equal to the original number.

Example : Input :
L = 1
R = 1000
Output :
1 2 145
Explanation :
Only 1, 2 and 145 are the strong numbers from 1 to 1000 because
1! = 1,
2! = 2, and
(1! + 4! + 5!) = 145

Algorithm :

The idea is to iterate from [L, R] and check if any number between the range is strong number or not.
If yes then print the corresponding number, else check for the next number.

Time and Space Complexity :

Time Complexity : O(n)
Space Complexity : O(1)

Code in Java

Run

class Main{
 
    static int[] factorial = { 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880 };
 
    public static boolean isStrong(int N)
    {
 
        String num = Integer.toString(N);
 
        int sum = 0;
 
        for (int i = 0;
            i < num.length(); i++) {
            sum += factorial[Integer.parseInt(num.charAt(i) + "")];
        }
 
        return sum == N;
    }
 
    public static void printStrongNumbers(int L, int R)
    {
 
        for (int i = L; i <= R; i++) {

            if (isStrong(i)) {
                System.out.print(i + " ");
            }
        }
    }
 
    // Driver Code
    public static void main(String[] args) 
    {
        int L=28, R = 890;
 
        // Function Call
        printStrongNumbers(L, R);
    }
}