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  1. class ReverseFactorial
  2. {
  3. 	public static void unfactorialize(int input) {
  4.  
  5.     double x = input;
  6.     int f = 2;
  7.  
  8.     while(x > 1) {
  9.         x = x / f;
  10.         if(x == 1) {
  11.             System.out.println(input + " = " + f + "!");   //check for x == 1 BEFORE you increase f
  12.             return;
  13.         }
  14.         f++;
  15.     }
  16.     System.out.println(input + "  NONE");    //if the program reaches this point, it has left while loop
  17. }                                            //and there is no reverse factorial
  18.  
  19.     public static void main(String[] args) {
  20.         unfactorialize(120);
  21.         unfactorialize(150);
  22.         unfactorialize(3628800);
  23.         unfactorialize(479001600);
  24.         unfactorialize(6);
  25.         unfactorialize(18);
  26.     }
  27. }
Success #stdin #stdout 0.05s 711168KB
comments ()
stdin 
Standard input is empty
stdout 
120 = 5!
150  NONE
3628800 = 10!
479001600 = 12!
6 = 3!
18  NONE
https://ideone.com/dnBnIE
language:
Java (HotSpot 12)
created:
8 years ago
visibility:
public

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