1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
#include <bits/stdc++.h>

using namespace std;

bool is_sorted(vector<int> const& v) {
    for (size_t i = 1; i < v.size(); ++i) {
        if (v[i - 1] >= v[i])
            return false;
    }
    return true;
}

void simulate(vector<int> &p, vector<int> const& rnd) {
    vector<int> vals;
    vals.reserve(rnd.size());

    for (int pos : rnd)
        vals.push_back(p[pos - 1]);

    for (int pos : rnd) {
        p[pos - 1] = vals.back();
        vals.pop_back();
    }
}

bool is_correct(vector<int> p, vector<vector<int>> const& r) {
    for (auto const &rnd : r)
        simulate(p, rnd);
    return is_sorted(p);
}

void print(vector<int> const& v) {
    cout << v.size() << '\n';
    for (int i : v)
        cout << i << ' ';
    cout << '\n';
}

using trans_t = pair<int, int>;
using transpositions_t = vector<trans_t>;
using cycle_t = vector<int>;

vector<cycle_t> cycle_decomposition(vector<int> const& p) {
    vector<cycle_t> r;

    set<int> not_visited(p.begin(), p.end());
    while (not not_visited.empty()) {
        int s, i;
        auto beg = not_visited.begin();
        s = i = *beg;
        not_visited.erase(beg);

        cycle_t c {i};
        while (p[i] != s) {
            i = p[i];
            c.push_back(i);
            not_visited.erase(i);
        }

        r.push_back(c);
    }

    return r;
}

pair<vector<int>, vector<int>> unzip(vector<pair<int, int>> const &zipped) {
    size_t n = zipped.size();
    vector<int> fst, snd;
    fst.reserve(n);
    snd.reserve(n);

    for (auto [a, b] : zipped) {
        fst.push_back(a);
        snd.push_back(b);
    }

    return make_pair(fst, snd);
}

vector<int> encode_trans(transpositions_t const& ts) {
    auto [a, b] = unzip(ts);
    reverse(a.begin(), a.end());
    a.insert(a.end(), b.begin(), b.end());
    for (int &i : a)
        ++i;
    return a;
}

vector<vector<int>> transpositions(vector<cycle_t> const &cycles) {
    transpositions_t fst, snd;

    for (auto const& cycle : cycles) {
        if (cycle.size() == 2) {
            trans_t t = make_pair(cycle.front(), cycle.back());
            fst.push_back(t);
        }
        if (cycle.size() <= 2)
            continue;
        // cycle has length greater than 2

        int n = cycle.size();
        for (int l = 0, r = n - 2; l < r; )
            fst.push_back(make_pair(cycle[l++], cycle[r--]));
        for (int l = 0, r = n - 1; l < r; )
            snd.push_back(make_pair(cycle[l++], cycle[r--]));
    }

    vector<vector<int>> r;
    r.reserve(2);

    vector<int> a = encode_trans(fst), b = encode_trans(snd);
    if (not a.empty())
        r.push_back(a);
    if (not b.empty())
        r.push_back(b);

    return r;
}

void sol(vector<int> const& p) {
    auto init_cycles = cycle_decomposition(p);
    vector<vector<int>> r = transpositions(init_cycles);
    // assert(is_correct(p, r));

    cout << r.size() << '\n';
    for (auto const& v : r)
        print(v);
}

// input and setup
void solve() {
    int n;
    cin >> n;
    vector<int> a(n);

    {
        for (int &i : a)
            cin >> i;
        // a is input

        vector<int> h = a;
        sort(h.begin(), h.end());
        // h = sorted(a)

        map<int, int> m;
        for (int i = 0; i < n; ++i)
            m[h[i]] = i;
        // m is mapping of values from a onto [0..n-1]

        for (int &i : a)
            i = m[i];
    } // a is scaled to [0..n-1], can be treated as a permutation

    sol(a);
}

int main() {
    ios_base::sync_with_stdio(false), cin.tie(nullptr);
    solve();
    return 0;
}