Question

language use : c++

Correct Tower application to move the disks from the pin on the left to the pin on the right. Hint: draw the motion of th disks for a small set "say three" and walk your way through the recursion. #include <iostream> using namespace std; void towers(int,char,char,char); int main() int num; cout << "Number of disks: "; cin >> num; cout << "Sequences begin here \n"; towers(num, 'A', 'B! "C"); return 0; void towers(int num, char frompeg, char topeg,char auxpe if(num == 1) cout << "Move disk 1 from " << frompeg << " to peg" a topeg << endl; return; towers(num - 1, frompeg, auxpeg, topeg): cout << "Move disk" << num << "from peg" << frompe towers(num 1, auxpeg, topeg, frompeg): "to peg" << topeg << endl;

Answer 1

Note: Please read the full answer carefully. I know it's a little long but I need to explain the problem to you. I've tried solving the puzzle myself using the output of this program.And it worked!!

Answer:

I assume that this program is made for solving the mathematical puzzle known as "Tower of Hanoi". In this puzzle there are three towers/poles/pins and we have to transfer the disks from Tower 1(which is on the left) to Tower 3(which is on the right). The only rule that we need to follow for solving this puzzle is : "We cannot put/place a big disk on the top of a small one".

Now coming to the question. In the question, the three towers are named A,B and C. A represent the Source Tower (Tower from which the Disks needs to get transferred). B represents the Auxilary Tower (Tower that will be used for temporarily holding the Disks) and C represents the Destination Tower (Tower to which the Disks will be transferred).

The code provided above is almost correct. It can be corrected in the following two ways.

Method 1. By doing a little change while calling the function towers() in the main() function:

In the above code we're passing the following values while calling the towers() function. num for number of disk. 'A' for source tower, 'B' for Destination tower and 'C' for Auxilary tower. I hope you've figured out the problem till now. If you haven't let me help you out. We're Passing 'B' as the Destination tower and 'C' as the Auxilary tower. Whereas we should be passing 'B' as the Auxilary Tower and 'C' as the Destination Tower.

We can get the correct output by interchanging the values of 'B' and 'C' while calling the towers() function in the main() function. So the correct way of the function call should be: towers(num,'A','C','B');

The program will look like this if we made this change to the code:

#include <iostream>
using namespace std;
void towers(int, char, char,char);
int main()
{
int num;
cout<<"Number of disks: ";
cin>>num;
cout<<"Sequence begin here\n";
towers(num, 'A', 'C', 'B'); //the only change is made here.
return 0;
}

void towers(int num, char frompeg,char topeg, char auxpeg)
{
if (num == 1)
{
cout << "Move disk 1 from peg "<<frompeg<<" to peg " << topeg<<endl;
return;
}
towers(num - 1, frompeg, auxpeg, topeg);
cout << "Move disk " << num << " from peg " << frompeg <<" to peg " << topeg << endl;
towers(num - 1, auxpeg, topeg, frompeg);
}

Here's a screenshot of Output from the sample run:

File Edit View Terminal Tabs Help $ ./TOHanoi Number of disks: 4 Sequence begin here Move disk 1 from peg A to peg B Move disk 2 from peg A to peg Move disk 1 from peg B to peg C Move disk 3 from peg A to peg B Move disk 1 from peg C to peg A Move disk 2 from peg C to peg Move disk 1 from peg A to peg B Move disk 4 from peg A to peg C Move disk i from peg B to peg C Move disk 2 from peg B to peg A Move disk 1 from peg C to peg A Move disk 3 from peg B to peg C Move disk 1 from peg A to peg B Move disk 2 from peg A to peg C Move disk i from peg B to peg C $1 MUUMMUSCUOLO

Method 2: By changing the function definition as follows:

If you don't want to change the order of the arguments then you'll need to change the order of the parameters in the function definition.

Here's the modified code:

#include<iostream>
using namespace std;
void towers(int, char, char, char);
int main()
{
int num;
cout<<"Number of Disks: ";
cin>>num;
cout<<"Sequence begin here:\n";
towers(num,'A','B','C');
return 0;
}
void towers(int num,char frompeg, char auxpeg,char topeg) //change 1
{
   if(num==1)//no change
   {
       cout<<"Move Disk 1 from peg "<<frompeg<<" to peg "<<topeg<<endl;
       return;
   }

   towers(num-1,frompeg,topeg,auxpeg); //change 2
   cout<<"Move Disk "<<num<<" from peg "<<frompeg<<" to peg "<<topeg<<endl;
   towers(num-1,auxpeg,frompeg,topeg); //change 3
}

Here's the screenshot of output from the sample run:

File Edit View Terminal Tabs Help $ ./TOHanoil Number of Disks: 4 Sequence begin here: Move Disk 1 from peg A to peg Move Disk 2 from peg A to peg C Move Disk 1 from peg B to peg Move Disk 3 from peg A to peg B Move Disk 1 from peg C to peg A Move Disk 2 from peg C to peg B Move Disk 1 from peg A to peg B Move Disk 4 from peg A to peg C Move Disk 1 from peg B to peg C Move Disk 2 from peg B to peg A Move Disk 1 from peg C to peg A Move Disk 3 from peg B to peg C Move Disk 1 from peg A to peg B Move Disk 2 from peg A to peg C Move Disk 1 from peg B to peg C MUUSMUUSSUOLO $

As you can see both ouput are similar. And both of them provide the correct output.

If you have any questions regarding the answer, or have any problem in understanding any part of it; please let me know in the comments. I'll get back to you ASAP.

Thanks.