Tuesday, 29 March 2016

Hanoi puzzle (using Recussion)


The Tower of Hanoi or Towers of Hanoi is a mathematical game or puzzle
It consists of three rods, and a number of disks of different sizes which can slide onto any rod. The puzzle starts with the disks in a neat stack in ascending order of size on one rod, the smallest at the top, thus making a conical shape.
The objective of the puzzle is to move the entire stack to another rod, obeying the following rules :
  • Only one disk may be moved at a time. 
  • Each move consists of taking the upper disk from one of the rods and sliding it onto another rod, on top of the other disks that may already be present on that rod. 
  • No disk may be placed on top of a smaller disk.

public class HanoiTower {
  static int nDisks = 3;
  public static void main(String[] args) {
   hanoiTower(nDisks, 'A', 'B', 'C');
  }
  public static void hanoiTower(int topN, char src, char inter, char dest) {
    if (topN == 1) {
      System.out.println("Disk 1 from " + src + " to " + dest);
    } else {
      // src to inter
      hanoiTower(topN - 1, src, dest, inter);
      // move bottom
      System.out.println("Disk " + topN + " from " + src + " to " + dest);
      // inter to dest
      hanoiTower(topN - 1, inter, src, dest);
    }
  }
}


Disc 1 from A to C
Disc 2 from A to B
Disc 1 from C to B
Disc 3 from A to C
Disc 1 from B to A
Disc 2 from B to C
Disc 1 from A to C

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