hanoi.cpp

#include <stack>
#include <cassert>

using namespace std;

namespace hanoi {

static void move(stack<int>& from, stack<int>& to)
{
    assert(!from.empty());
    assert(to.empty() || to.top() > from.top());
    to.push(from.top());
    from.pop();
}

static void move_substack(stack<int>& from, stack<int>& to, stack<int>& temp, int depth)
{
    if (depth <= 0)
        return;

    move_substack(from, temp, to, depth - 1);
    move(from, to);
    move_substack(temp, to, from, depth - 1);
}

static void move(stack<int>& from, stack<int>& to, stack<int>& temp)
{
    move_substack(from, to, temp, from.size());
}

}

int main()
{
    stack<int> from, to, temp;
    for (int i = 5; i >= 1; i--)
        from.push(i);
    
    hanoi::move(from, to, temp);

    assert(from.empty());
    assert(temp.empty());
    for (int i = 1; i <= 5; i++) {
        assert(to.top() == i);
        to.pop();
    }
    assert(to.empty());

    return 0;
}