181 lines
3.7 KiB
C++
181 lines
3.7 KiB
C++
/* Problem URL: https://codeforces.com/problemset/problem/2112/D */
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#include <bits/stdc++.h>
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#include <ext/pb_ds/assoc_container.hpp>
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#include <ext/pb_ds/tree_policy.hpp>
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using namespace std;
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using namespace __gnu_pbds;
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template <class T, class comp = less<>>
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using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;
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#define V vector
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#define rmin(a, b) a = min(a, b)
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#define rmax(a, b) a = max(a, b)
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#define rep(i, lim) for (int i = 0; i < (lim); i++)
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#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
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#define repv(i, v) for (auto &i : (v))
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#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
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#define sortv(v) sort(v.begin(), v.end())
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#define all(v) (v).begin(), (v).end()
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using vi = vector<int>;
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using vvi = vector<vi>;
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using vvvi = vector<vvi>;
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using vvvvi = vector<vvvi>;
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using ll = long long;
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using vl = vector<ll>;
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using vvl = vector<vl>;
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using vvvl = vector<vvl>;
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using vvvvl = vector<vvvl>;
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template<class v>
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auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
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os << vec[0];
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for (size_t i = 1; i < vec.size(); i++) {
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os << ' ' << vec[i];
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}
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os << '\n';
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return os;
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}
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template<class v>
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auto operator>>(istream &is, vector<v> &vec)->istream& {
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for (auto &i : vec) {
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is >> i;
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}
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return is;
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}
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template<class v>
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auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
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for (auto &i : vec) {
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os << i[0];
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for (size_t j = 1; j < i.size(); j++) {
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os << ' ' << i[j];
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}
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os << '\n';
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}
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return os;
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}
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template<class v>
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auto operator>>(istream &is, vector<vector<v>> &vec)->istream& {
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for (auto &i : vec) {
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for (auto &j : i) {
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is >> j;
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}
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}
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return is;
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}
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const int oo = INT32_MAX >> 1;
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const ll OO = INT64_MAX >> 1;
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void pre()
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{
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}
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#define TEST 1
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void solve()
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{
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int n;
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cin >> n;
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vvi graph(n);
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rep(i, n - 1) {
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int a, b;
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cin >> a >> b;
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a--, b--;
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graph[a].push_back(b);
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graph[b].push_back(a);
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}
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V<pair<int, int>> edges;
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pair<int, int> c1;
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pair<int, int> c2;
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int dc = -1;
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function<bool(int, int, int)> dfs = [&](int i, int p, int d) {
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bool valid = false;
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repv(j, graph[i]) {
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if (j == p) {
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continue;
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}
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valid = valid || graph[i].size() >= 2;
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if (d & 1) {
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edges.emplace_back(j + 1, i + 1);
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} else {
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edges.emplace_back(i + 1, j + 1);
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}
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if (dfs(j, i, d + 1 - valid) && dc == -1) {
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dc = d;
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c1 = {i + 1, j + 1};
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c2 = {j + 1, graph[j][0] == i ? graph[j][1] + 1 : graph[j][0] + 1};
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// edges.pop_back();
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edges.pop_back();
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edges.pop_back();
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}
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}
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return valid;
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};
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dfs(0, 0, 0);
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if (dc == -1) {
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edges.clear();
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dfs(n - 1, n - 1, 0);
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if (dc == -1) {
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edges.clear();
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dfs(n - 2, n - 2, 0);
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if (dc == -1) {
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edges.clear();
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dfs(1, 1, 0);
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if (dc == -1) {
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cout << "NO\n";
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return;
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}
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}
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}
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}
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cout << "YES\n";
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if (dc & 1) {
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repv(i, edges) {
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swap(i.first, i.second);
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}
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}
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repv(i, edges) {
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cout << i.first << ' ' << i.second << '\n';
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}
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cout << c1.first << ' ' << c1.second << '\n';
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cout << c2.first << ' ' << c2.second << '\n';
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}
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int main()
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{
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ios::sync_with_stdio(false);
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cin.tie(nullptr);
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pre();
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int t;
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(TEST && cin >> t) || (t = 1);
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while (t--) {
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solve();
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}
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}
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