A bunch new problems

Refact.ai Match 1 (Codeforces Round 985)/D. Cool Graph.cpp

@@ -0,0 +1,256 @@
+/* Problem URL: https://codeforces.com/problemset/problem/2029/D */
+
+#include <bits/stdc++.h>
+#include <ext/pb_ds/assoc_container.hpp>
+#include <ext/pb_ds/tree_policy.hpp>
+
+using namespace std;
+using namespace __gnu_pbds;
+
+template <class T, class comp = less<>>
+using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;
+
+#define V vector
+
+#define rmin(a, b) a = min(a, b)
+#define rmax(a, b) a = max(a, b)
+
+#define rep(i, lim) for (int i = 0; i < (lim); i++)
+#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
+
+#define repv(i, v) for (auto &i : (v))
+#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
+#define sortv(v) sort(v.begin(), v.end())
+#define all(v) (v).begin(), (v).end()
+
+using vi = vector<int>;
+using vvi = vector<vi>;
+using vvvi = vector<vvi>;
+using vvvvi = vector<vvvi>;
+
+using ll = long long;
+
+using vl = vector<ll>;
+using vvl = vector<vl>;
+using vvvl = vector<vvl>;
+using vvvvl = vector<vvvl>;
+
+template<class v>
+auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
+    os << vec[0];
+    for (size_t i = 1; i < vec.size(); i++) {
+        os << ' ' << vec[i];
+    }
+    os << '\n';
+    return os;
+}
+
+template<class v>
+auto operator>>(istream &is, vector<v> &vec)->istream& {
+    for (auto &i : vec) {
+        is >> i;
+    }
+    return is;
+}
+
+template<class v>
+auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
+    for (auto &i : vec) {
+        os << i[0];
+        for (size_t j = 1; j < i.size(); j++) {
+            os << ' ' << i[j];
+        }
+        os << '\n';
+    }
+    return os;
+}
+
+template<class v>
+auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
+    for (auto &i : vec) {
+        for (auto &j : i) {
+            is >> j;
+        }
+    }
+    return is;
+}
+
+const int oo = INT32_MAX >> 1;
+const ll OO = INT64_MAX >> 1;
+
+
+void pre()
+{
+
+}
+
+#define TEST 1
+
+void solve()
+{
+    int n, m;
+    cin >> n >> m;
+
+    vvi graph(n);
+    while (m--) {
+        int a, b;
+        cin >> a >> b;
+        a--, b--;
+        graph[a].push_back(b);
+        graph[b].push_back(a);
+    }
+
+    V<bool> vis(n);
+    V<bool> frame(n);
+    vi cur(n);
+
+    set<pair<int, int>> rem;
+    vvi loops;
+    int end = -1;
+
+    function<bool(int, int)> dfs = [&](int i, int p) {
+        vis[i] = true;
+        frame[i] = true;
+
+        for (int &k = cur[i]; k < graph[i].size(); k++) {
+            int j = graph[i][k];
+            
+            if (j == p) {
+                continue;
+            }
+
+            if (rem.count({i, j})) {
+                continue;
+            }
+
+            if (frame[j]) {
+                end = j;
+                loops.emplace_back();
+                loops.back().push_back(i);
+                frame[i] = false;
+                vis[i] = false;
+                rem.emplace(i, j);
+                rem.emplace(j, i);
+                return true;
+            }
+
+            if (vis[j]) {
+                continue;
+            }
+            
+            if (dfs(j, i)) {
+                loops.back().push_back(i);
+                rem.emplace(i, j);
+                rem.emplace(j, i);
+                if (end != i) {
+                    frame[i] = false;
+                    vis[i] = false;
+                    return true;
+                }
+            }
+        }
+
+        frame[i] = false;
+        return false;
+    };
+
+    rep(i, n) {
+        if (vis[i]) {
+            continue;
+        }
+        dfs(i, i);
+    }
+
+    int c = 0;
+
+    V<tuple<int, int, int>> ans;
+    repv(j, loops) {
+        nrep(i, 2, j.size()) {
+            ans.emplace_back(j[0] + 1, j[i - 1] + 1, j[i] + 1);
+        }
+    }
+
+    auto printans = [&]() {
+        cout << ans.size() << '\n';
+        for (auto [i, j, k] : ans) {
+            cout << i << ' ' << j << ' ' << k << '\n';
+        }
+    };
+
+    vvi act(n);
+    rep(i, n) {
+        repv(j, graph[i]) {
+            if (rem.count({i, j})) {
+                continue;
+            }
+            act[i].push_back(j);
+            c++;
+        }
+    }
+
+    if (c == 0) {
+        printans();
+        return;
+    }
+
+    fill(all(vis), false);
+    vi g(n);
+    int gg = 0;
+    set<int> ev;
+
+    function<void(int)> func = [&](int i) {
+        vis[i] = true;
+        g[i] = gg;
+
+        repv(j, act[i]) {
+            if (vis[j]) {
+                continue;
+            }
+
+            func(j);
+        }
+    };
+
+    rep(i, n) {
+        if (vis[i]) {
+            continue;
+        }
+        func(i);
+        gg++;
+    }
+
+    int a1 = -1;
+    int a2 = -1;
+    rep(i, n) {
+        if (act[i].size() > 0) {
+            a1 = i;
+            a2 = act[i][0];
+            ev.insert(g[i]);
+            break;
+        }
+    }
+
+    rep(i, n) {
+        if (!ev.count(g[i])) {
+            ans.emplace_back(a1 + 1, a2 + 1, i + 1);
+            ev.insert(g[i]);
+            a1 = i;
+        }
+    }
+
+    printans();
+}
+
+int main()
+{
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    pre();
+
+    int t;
+    (TEST && cin >> t) || (t = 1);
+    while (t--) {
+        solve();
+    }
+}