Why does my C program stop running?

Question

Programming

Why when I run this program

#include <stdio.h>


void hanoi(int height, int start, int finish)
{
    if (height == 1) {
        printf("%d %d\n", start, finish);
    } else {
        int tmp = 6 - start - finish;
        hanoi(height - 1, start, tmp);
        printf("%d %d\n", start, finish);
        hanoi(height - 1, tmp, finish);
    }
}

int main()
{
    int k;
    scanf("%d",k);
    hanoi(k,1,2);

    return 0;
}

I enter one number and the program stops working? And how to fix it?

Answer 1

Because in scanf you need to pass the address of the variable - &k. Yes, initialize the variable itself.

Answer 2

1. You have already been told about scanf.
(i.e. your program doesn't "stop" as you expected - it just crashes ;-) )
2. You can forward it:
So it's much clearer and more logical than some kind of arithmetic with subtractions.
3. And, if you are already having fun with recursion, then it is more logical to write it like this:

int tmp = start ^ finish;
hanoi( height - 1, start, tmp );
hanoi( 1, start, finish );
hanoi( height - 1, tmp, finish );