Printing count with static int in java

Question

I am trying to display the count of moves within a program that solves the Tower of Hanoi puzzle, but it keeps displaying the count more than once as seen in my output below

Input the number of rings: 2
Towers of Hanoi with 2 rings 
1
3
3

I want it to only display the number 3 once, instead of 1, 3, 3. Here is my code below (For my assignment,I have to declare a static int count).

  import java.util.Scanner;
  public class Towers
  {
  static int count;
  public static void doTowers(
     int n,              // Number of rings to move
     int startPeg,       // Peg containing rings to move
     int auxPeg,         // Peg holding rings temporarily
     int endPeg ) // Peg receiving rings being moved
     {

  boolean b = true;

  while(b){ 
  if (n == 1){ // Base case - Move one ring
   count = count + 1;
   b = true;
  }
   if (n == 0){
    b = false;
  }
  else{
  // Move n - 1 rings from starting peg to auxiliary peg
  doTowers(n - 1, startPeg, endPeg, auxPeg);
  count = count + 1;
  b = true;



  // Move n - 1 rings from auxiliary peg to ending peg
  doTowers(n - 1, auxPeg, startPeg, endPeg);
 }
 }
  }





public static void main(String[] args)

{
Scanner conIn = new Scanner(System.in);
// Number of rings on starting peg.
int n;       
System.out.print("Input the number of rings: ");
if (conIn.hasNextInt())
  n = conIn.nextInt();
else
{
  System.out.println("Error: you must enter an integer.");
  System.out.println("Terminating program.");
  return;
}

if (n < 1)
{
  System.out.println("Error: you must enter an integer >= 1.");
  System.out.println("Terminating program.");
  return;
}

System.out.println("Towers of Hanoi with " + n + " rings ");
doTowers(n, 1, 2, 3);
System.out.println("This takes " + count + " moves.");

} }

Because your method is recursive. Expose a getter method for count, and print the result in main() after call to doTowers(). — OldProgrammer
– OldProgrammer, Commented Feb 25, 2017 at 20:19

Darshan Mehta · Accepted Answer · 2017-02-25 20:20:25Z

1

Instead of having System.out.println(count); inside doTowers method you can print the count in main, once the method is executed, e.g.:

doTowers(n, 1, 2, 3);
System.out.println(count);

This will not print count multiple times (the reason why it happends in your case is because doTowers makes a recursive call and has sysout statement inside it, so each call results in a sysout).

answered Feb 25, 2017 at 20:20

Darshan Mehta

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2 Comments

user7578222 Over a year ago

This worked perfectly, thank you! Any tips on how I can go about modifying the program so that it keeps running and asking for a number of rings until he enters a number less than 0?

Darshan Mehta Over a year ago

You can write a do..while loop which would keep taking a number from user until a condition is not met. An example here: stackoverflow.com/questions/22733632/…

Java Mantr · Accepted Answer · 2017-02-25 20:28:03Z

0

When you call a function recursively, like you have, the return will execute the rest of the function body. Its like pushing into and popping out of a stack

answered Feb 25, 2017 at 20:28

Java Mantr

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