#include <bits/stdc++.h> using namespace std; struct cycle { vector<int> v; auto first() { vector<pair<int,int>> ret; if (v.size() % 2 == 1) { for (int i = 0; i < v.size()/2; i++) { ret.push_back({v[i], v[v.size()-1-i]}); } } else { for (int i = 0; i < v.size()/2; i++) { ret.push_back({v[i], v[v.size()-1-i]}); } } return ret; } auto second() { vector<pair<int,int>> ret; if (v.size() % 2 == 1) { for (int i = 0; i < v.size()/2; i++) { int a = v[i+1]; int b = v[v.size()-i-1]; if (a != b) ret.push_back({v[i+1], v[v.size()-1-i]}); } } else { for (int i = 0; i < v.size()/2; i++) { int a = v[i+1]; int b = v[v.size()-i-1]; if (a != b) ret.push_back({v[i+1], v[v.size()-1-i]}); } } return ret; } }; int main() { int n; cin >> n; vector<pair<int,int>> a(n); for (int i = 0; i < n; i++) { cin >> a[i].first; a[i].second = i; } sort(a.begin(), a.end()); vector<int> p(n); for (int i = 0; i < n; i++) { p[a[i].second] = i; } vector<int> vis(n); vector<cycle> cycles; for (int i = 0; i < n; i++) { if (!vis[i]) { int cur = i; vector<int> v; while (!vis[cur]) { v.push_back(cur+1); vis[cur] = 1; cur = p[cur]; } cycles.push_back({v}); } } vector<pair<int,int>> first; for (auto& cycle : cycles) { auto a = cycle.first(); for (auto pa : a) { first.push_back({pa}); } } vector<pair<int,int>> second; for (auto& cycle : cycles) { auto a = cycle.second(); for (auto pa : a) { second.push_back(pa); } } if (first.empty()) { cout << "0\n"; } else { if (second.empty()) { cout << "1\n"; } else cout << "2\n"; cout << first.size() * 2 << '\n'; for (int i = 0; i < first.size(); i++) { cout << first[i].first << ' '; } for (int i = first.size()-1; i >= 0; i--) { cout << first[i].second << ' '; } if (second.size()) { cout << '\n'; cout << second.size() * 2 << '\n'; for (int i = 0; i < second.size(); i++) { cout << second[i].first << ' '; } for (int i = second.size()-1; i >= 0; i--) { cout << second[i].second << ' '; } } } return 0; }
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 | #include <bits/stdc++.h> using namespace std; struct cycle { vector<int> v; auto first() { vector<pair<int,int>> ret; if (v.size() % 2 == 1) { for (int i = 0; i < v.size()/2; i++) { ret.push_back({v[i], v[v.size()-1-i]}); } } else { for (int i = 0; i < v.size()/2; i++) { ret.push_back({v[i], v[v.size()-1-i]}); } } return ret; } auto second() { vector<pair<int,int>> ret; if (v.size() % 2 == 1) { for (int i = 0; i < v.size()/2; i++) { int a = v[i+1]; int b = v[v.size()-i-1]; if (a != b) ret.push_back({v[i+1], v[v.size()-1-i]}); } } else { for (int i = 0; i < v.size()/2; i++) { int a = v[i+1]; int b = v[v.size()-i-1]; if (a != b) ret.push_back({v[i+1], v[v.size()-1-i]}); } } return ret; } }; int main() { int n; cin >> n; vector<pair<int,int>> a(n); for (int i = 0; i < n; i++) { cin >> a[i].first; a[i].second = i; } sort(a.begin(), a.end()); vector<int> p(n); for (int i = 0; i < n; i++) { p[a[i].second] = i; } vector<int> vis(n); vector<cycle> cycles; for (int i = 0; i < n; i++) { if (!vis[i]) { int cur = i; vector<int> v; while (!vis[cur]) { v.push_back(cur+1); vis[cur] = 1; cur = p[cur]; } cycles.push_back({v}); } } vector<pair<int,int>> first; for (auto& cycle : cycles) { auto a = cycle.first(); for (auto pa : a) { first.push_back({pa}); } } vector<pair<int,int>> second; for (auto& cycle : cycles) { auto a = cycle.second(); for (auto pa : a) { second.push_back(pa); } } if (first.empty()) { cout << "0\n"; } else { if (second.empty()) { cout << "1\n"; } else cout << "2\n"; cout << first.size() * 2 << '\n'; for (int i = 0; i < first.size(); i++) { cout << first[i].first << ' '; } for (int i = first.size()-1; i >= 0; i--) { cout << first[i].second << ' '; } if (second.size()) { cout << '\n'; cout << second.size() * 2 << '\n'; for (int i = 0; i < second.size(); i++) { cout << second[i].first << ' '; } for (int i = second.size()-1; i >= 0; i--) { cout << second[i].second << ' '; } } } return 0; } |