Recursion please explain this

[Would]

hey someone posted towers of hanoi code on here.. I have this assignment in my programming class now.. I obviously can take this code and modify it but i just want to understand how this works I cant turn this in not knowing whats going on here. Could someone please explain to me what is going on when the program enters hanoi (nDisks - 1, pegA, pegC, pegB); that function? What is the purpose for switching the order of pegA, B, and C? this is the entire code..

#include <iostream>
using namespace std;
void hanoi (int nDisks, int pegA, int pegB, int pegC);
int count = 0;
 
int main ()
{
    int n;
 
    cout << "Input number of disks: ";
    cin >> n;
 
    hanoi (n, 1, 2, 3);
    cout<<"Number of moves required: "<<count<<endl;
 
    return 0;
}
 
void hanoi (int nDisks, int pegA, int pegB, int pegC)
{
    if (nDisks>0) 
    {
        hanoi (nDisks - 1, pegA, pegC, pegB);
 
 
        cout << "Move disk from peg " << pegA << " to peg " << pegC << endl;
 
        hanoi( nDisks-1, pegB, pegA, pegC);
 
        count++;
    }
}

[Ganon11]

Let me suggest that you get rid of this code, now, and write your own. TSDN doesn't support plagiarism, and your teacher might get wise as give you a 0 for cheating.

The best way for you to understand how a program works is to write it on your own. Come up with a general solution for solving a TOH puzzle, and then turn that solution into an algorithm.

[Would]

Did I anywhere suggest that I was planning on turning this code in? I posted the code asking if someone can explain to me how this is actually working. Then after gaining an understanding I can write my own code.. thanks for the help though

[Ganon11]

I obviously can take this code and modify it but i just want to understand how this works I cant turn this in not knowing whats going on here.

By this, I thought you meant you would be turning it in, but not until you understood it. Sorry for any misunderstanding and/or harshness on my part.

[Would]

By this, I thought you meant you would be turning it in, but not until you understood it. Sorry for any misunderstanding and/or harshness on my part.

No, I may have worded that wrong. I simply got the code off of here earlier today in an attempt to debug and try to figure out how it works. I just dont understand what is going on with the two function calls.. What do the variables in the arguement actually do? ie. pegA, pegB, pegC.. and the n-1? I just cant grasp what is going on here.

[Masood Ali]

hey someone posted towers of hanoi code on here.. I have this assignment in my programming class now.. I obviously can take this code and modify it but i just want to understand how this works I cant turn this in not knowing whats going on here. Could someone please explain to me what is going on when the program enters hanoi (nDisks - 1, pegA, pegC, pegB); that function? What is the purpose for switching the order of pegA, B, and C? this is the entire code..

#include <iostream>
using namespace std;
void hanoi (int nDisks, int pegA, int pegB, int pegC);
int count = 0;
 
int main ()
{
    int n;
 
    cout << "Input number of disks: ";
    cin >> n;
 
    hanoi (n, 1, 2, 3);
    cout<<"Number of moves required: "<<count<<endl;
 
    return 0;
}
 
void hanoi (int nDisks, int pegA, int pegB, int pegC)
{
    if (nDisks>0) 
    {
        hanoi (nDisks - 1, pegA, pegC, pegB);
 
 
        cout << "Move disk from peg " << pegA << " to peg " << pegC << endl;
 
        hanoi( nDisks-1, pegB, pegA, pegC);
 
        count++;
    }
}

Actually this code works on the principle
To move n disks from one source peg to the destination peg, U hav to first move n-1 disks to the middle peg using it as a temporary peg, and then move the last disk from the source to destination peg and then continue in this way till all the disks hav been moved.

Example":

to move 3 disks from source (peg 1) to the destination (peg3), U hav to first move 2 disks to the middle peg (peg2), using it as a temporary peg...

But now to move 2 disks from peg1 to peg2, U hav to move 1 disk from peg1 to peg 3 and then one from peg1 to peg2...
So the chain continues till all disks hav been moved..
Hope U understand. if not then let me know at <email removed>

[Would]

Well, I have figured it out and written my own version of the code.. I sat here trying to keep my eyes open for a couple of hours over this one.. I came to the conclusion that in my move function i am originally wanting to move 1 disk which would be disk -1 from peg1 to peg3 using peg2 as the temp holding area... so in the function i arranged peg1, then peg3 to achieve this then peg2 at the end of the arguement.. did some output then after the top function quit when disks -1 was 0 the next function i had one final disk( i made this example with 2 disks) i wanted the final disk which was the top one to move from the holding position on peg2 to the final peg (peg3) so i arranged them like so in the function arguement.. in the order that i wanted things to happen on small scale.. and it seems to be correct for any size! Is that how i should be looking at it? Here is my code.. Keep in mind I had already edited some things on the first example code that I posted it was actually laid out differently so i didnt copy!

#include <iostream>
using namespace std;
void move( int disks, int peg1, int peg2, int peg3);
int count = 0;
 
void main()
{
    int disks = 0;
    cout<<"How many disks?"<<endl;
    cin>> disks;
    move( disks, 1, 2, 3);
    cout<<"Moves required: "<< count<<endl;
}
 
void move( int disks, int peg1, int peg2, int peg3)
{
    if(disks > 0)
    {
        move(disks - 1, peg1, peg3, peg2);
        cout<< peg1<< "-->" << peg3<<endl;
        move(disks -1, peg2, peg1, peg3);
        count++;
    }
}

[Ganon11]

It looks right to me, but for some reason it won't compile on my computer. Are you sure you can use void main()? My compiler wants it to be int main().

[Extremist]

Have you tried to make it int main ?
Just return 0.

Just a question ;-)

[Ganon11]

I did - that one of the things I had to do to make it C++worthy.

But my compiler is giving me trouble in declaring int count = 0; outside of main(). It says that main() and move() can't see count - it's undeclared.

[Extremist]

I did - that one of the things I had to do to make it C++worthy.

But my compiler is giving me trouble in declaring int count = 0; outside of main(). It says that main() and move() can't see count - it's undeclared.

That's funny, I ran it in Visual Studio, In linux and I ran it with a borland compiler and I didn't get any problems...

Whether it is void or int.

;-)

[Would]

Yeah, that is weird that you guys are having compiler troubles with this... Im using Crimson editor and borland as my compiler and it works.. I also ran it through in visual studio and didnt get problems. I'll mess around with it a little more.

[Would]

I did - that one of the things I had to do to make it C++worthy.

But my compiler is giving me trouble in declaring int count = 0; outside of main(). It says that main() and move() can't see count - it's undeclared.

That doesnt really make sense why main() or move() cant see count.. its a global variable?

[Ganon11]

Yeah, I copied your code exactly - all I changed was making main into int main(), adding a return 0 at the end (to match the int main()) and adding a system("PAUSE"); command to freeze the output, and it won't compile for me. How weird.