Tower of Hanoi.cpp

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
using namespace std;

#define read freopen("input.txt", "r", stdin)
#define write freopen("output.txt", "w", stdout)

#define pb push_back
#define ll long long
#define ull unsigned long long
#define ld long double
#define pii pair<int, int>
#define vi vector<int>
#define vii vector<pii>
#define mpi map<int, int>
#define si set<int>
#define vt vector
#define getline cout << '\n'
#define all(x) x.begin(), x.end()

#define FOR(i, a, b) for (long long int i = a; (b - i) * (a - i) <= 0 && (b > a ? b != i : b != a); b > a ? i++ : i--)
#define FOREACHR(it, m) for (auto it = m.rbegin(); it != m.rend(); it++)
#define FOREACH(it, m) for (auto it = m.begin(); it != m.end(); it++)
// #define FOREACH(it, m) for (auto it : m)

// #define IOS ios_base::sync_with_stdio(false)

#define scanset(s, n) \
    FOR(i, 0, n)      \
    {                 \
        int x;        \
        cin >> x;     \
        s.insert(x);  \
    }

template <class T, size_t size>
// scan array
void scan(T (&array)[size])
{
    for (size_t i = 0; i < size; ++i)
        cin >> array[i];
}
template <class T, size_t size>
// print array
void print(const T (&array)[size])
{
    for (size_t i = 0; i < size; ++i)
        cout << array[i] << " ";
}
template <class T, size_t size>
void println(const T (&array)[size])
{
    print(array);
    cout << endl;
}
template <class T>
// scan vector with size
void scan(T &x)
{
    for (size_t i = 0; i < x.size(); i++)
    {
        cin >> x[i];
    }
}
template <class T>
// print vector
void print(const T &t)
{
    for (size_t i = 0; i < t.size(); i++)
        cout << t[i] << endl;
}
template <class T>
void println(const T &t)
{
    print(t);
    cout << endl;
}
template <class T>
// print vector, set, ...
void __print_collection(T const &container)
{
    for (auto pos : container)
        cout << pos << " ";
}

void __print_pair(pair<int, int> p)
{
    cout << p.first << " " << p.second << "\n";
}
vector<pair<int, int>> steps;
void move(int a[3], int f, int t, int n)
{
    if (n == 1)
    {
        a[f]--;
        a[t]++;
        steps.push_back(pair<int, int>(f + 1, t + 1));
    }
    else
    {
        move(a, f, 3 - f - t, n - 1);
        move(a, f, t, 1);
        move(a, 3 - f - t, t, n - 1);
    }
}
int main()
{
    int step = 0;
    int a[3];
    cin >> a[0];
    move(a, 0, 2, a[0]);
    cout << steps.size() << endl;
    for (int i = 0; i < steps.size(); i++)
    {
        __print_pair(steps[i]);
    }
}