Strong Number Using Indirect recursion

Java/README.md

@@ -100,6 +100,7 @@ _add list here_
 - [Sieve of Eratosthenes](math/SieveOfEratosthenes.java)
 - [Catalan Number](math/CatalanNumber.java)
 - [Palindrome Number Using Recursion](math/PalindromeRecursion.java)
+- [Strong Number Using Recursion](math/check_strong_number.java)
 
 ## Dynamic Programming
 

Java/math/check_strong_number.java

@@ -0,0 +1,50 @@
+
+/*
+Checking for a strong number using indirect recursion
+Strong Number = 145
+1! + 4! + 5! =145
+sumOfFactorialOfDigit(int n) - extracts digit of n and calls factorial(n). Returns sum of factorial of digits
+factorial(n)- returns factorial of extracted digits passed in the argument
+*/
+
+import java.util.*;
+class check_strong_number {
+    /*recursive function for sum of factorial of digits*/
+    public static int sumOfFactorialOfDigit(int n)
+
+    {
+        if (n == 0)
+            return n;
+        else
+            return (factorial(n % 10) + sumOfFactorialOfDigit(n / 10));
+
+    }
+    /*recursive function to find the factorial of n */
+    public static int factorial(int n) {
+        if (n == 0)
+            return 1;
+        else
+            return (n * factorial(n - 1));
+    }
+
+    public static void main() {
+        Scanner sc = new Scanner(System.in);
+        System.out.print(" Enter Number. N = ");
+        int num = sc.nextInt();
+        if (num == sumOfFactorialOfDigit(num))
+            System.out.println(" It is a Strong Number");
+        else
+            System.out.println(" It is not a Strong Number");
+    }
+}
+
+/*
+Sample Input And Output :
+N = 145
+It is a Strong Number
+N = 534
+It is not a Strong Number
+
+Time Complexity : O(n)
+Space Complexity : 1
+*/