M3xr M3xr - 1 month ago 11
C Question

Why does my tower of hanoi algorithm not work?

I need to write a hanoi recursion algorithm with 3 parameters. This is what I got:

#include <stdio.h> #include <stdio.h>

void hanoi(int m, int i, int j);
void move(int start, int end);

int main(){
int n = 0;
int i = 1;
int j = 3;
printf("Enter how many disks you want to move: ");
scanf("%d", &n);
int m = n;
hanoi(m,i,j);

}

void hanoi(int m, int i, int j){
if (m==1)
{
move(i,j);
return;
}
hanoi(m-1,i,2);
move(i,j);
hanoi(m-1,2,j);

}

void move(int start, int end){
printf("A disk moves from position %d. to %d.\n", start,end);
}


The output for n=3 is the following:

Enter how many disks you want to move: 3
A disk moves from position 1. to 2.
A disk moves from position 1. to 2.
A disk moves from position 2. to 2.
A disk moves from position 1. to 3.
A disk moves from position 2. to 2.
A disk moves from position 2. to 3.
A disk moves from position 2. to 3.


I looked at other algorithms, I know there is tons of those for solving the goold old hanoi problem. However, they all have 4 parameters and use characters, whereas I would like to only use numbers and leave out the auxiliary tower parameter in my function. How can I fix it? For n=1 and n=2 the algorithm works fine.

Answer

Code needs to use the other peg, rather than 2 as commented by @Karoly Horvath

void hanoi(int m, int i, int j){    
    if (m==1) {
        move(i,j);
        return;
    }
    int Other_peg = (1+2+3) - i - j;
    hanoi(m-1,i,Other_peg);
    move(i,j);
    hanoi(m-1,Other_peg,j);
}