Java: Towers Of Hanoi

/*
Towers Of Hanoi.
There are three pegs: A, B and C. There are n disks. All disks are different in size.
The disks are initially stacked on peg A so that they increase in size from the top to the bottom.
The goal is to transfer the entire tower from the A peg to the C peg.
One disk at a time can be moved from the top of a stack either to an empty peg or to
a peg with a larger disk than itself on the top of its stack.

The method should return a sequence of disk moves, each move is a String with two letters (A, B or C)
corresponding to the peg the disk moves from and the peg it moves to.
For example, the move "AC" means that a top disk from peg A should be moved to peg C.
*/

1. import java.util.ArrayList;


2. importjava.util.List;


3.  


4.  


5. publicclassTowersOfHanoi {


6.  


7.     privatestaticList<String> list= newArrayList<String>();


8.     staticString a="A";


9.     staticString c="C";


10.     staticString b="B";


11.     staticString s="";


12.     publicstaticvoidmove(intn, intstartPole, intendPole) {


13.         if(n== 0){


14.           return;


15.         }


16.         intintermediatePole = 6- startPole - endPole;


17.         move(n-1, startPole, intermediatePole);


18.         System.out.println("Move "+n + " from "+ startPole + " to "+endPole);


19.         if(startPole==1)


20.             s=s+a;


21.         if(startPole==2)


22.             s=s+b;


23.         if(startPole==3)


24.             s=s+c;


25.         if(endPole==1)


26.             s=s+a;


27.          


28.         if(endPole==2)


29.             s=s+b;


30.         if(endPole==3)


31.             s=s+c;


32.          


33.         list.add(s);


34.         s="";


35.         move(n-1, intermediatePole, endPole);


36.       }


37.        


38.     publicstaticList<String> transferFromAtoC(intn) {


39.         /*


40.           Towers Of Hanoi.


41.           There are three pegs: A, B and C. There are n disks. All disks are different in size.


42.           The disks are initially stacked on peg A so that they increase in size from the top to the bottom.


43.           The goal is to transfer the entire tower from the A peg to the C peg.


44.           One disk at a time can be moved from the top of a stack either to an empty peg or to


45.           a peg with a larger disk than itself on the top of its stack.


46.  


47.           The method should return a sequence of disk moves, each move is a String with two letters (A, B or C)


48.           corresponding to the peg the disk moves from and the peg it moves to.


49.           For example, the move "AC" means that a top disk from peg A should be moved to peg C.


50.          */


51.          


52.         move(n, 1, 3);


53.         returnlist;


54.     }


55.       publicstaticvoidmain(String[] args) {


56.           List l1 = newArrayList();


57.         transferFromAtoC(1);


58.         System.out.println(list);


59.       }


60. }

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