A bunch new problems

Codeforces Round 954 (Div. 3)/F. Non-academic Problem.cpp

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+/* Problem URL: https://codeforces.com/problemset/problem/1986/F */
+
+#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;
+
+    V<V<pair<int, int>>> graph(n);
+    V<bool> rem(m);
+    while (m--) {
+        int a, b;
+        cin >> a >> b;
+        a--, b--;
+        graph[a].emplace_back(b, m);
+        graph[b].emplace_back(a, m);
+    }
+
+    V<bool> vis(n);
+    vi t(n);
+    vi mi(n);
+    int tim = 0;
+    int tt = 1;
+    function<int(int, int)> dfs = [&](int i, int p) {
+        vis[i] = true;
+        t[i] = tim++;
+        mi[i] = t[i];
+
+        for (auto [j, ind] : graph[i]) {
+            if (j == p) {
+                continue;
+            }
+
+            if (vis[j]) {
+                rmin(mi[i], t[j]);
+                continue;
+            }
+
+            rmin(mi[i], dfs(j, i));
+            if (mi[j] > t[i]) {
+                rem[ind] = true;
+                tt++;
+            }
+        }
+
+        return mi[i];
+    };
+
+    dfs(0, 0);
+
+    vl c(tt);
+    vi g(n);
+    vvi act(tt);
+    int cur = 0;
+    fill(all(vis), false);
+
+    function<void(int)> func = [&](int i) {
+        vis[i] = true;
+        g[i] = cur;
+        c[cur]++;
+        for (auto [j, ind] : graph[i]) {
+            if (vis[j] || rem[ind]) {
+                continue;
+            }
+
+            func(j);
+        }
+    };
+
+    rep(i, n) {
+        if (vis[i]) {
+            continue;
+        }
+        func(i);
+        cur++;
+    }
+
+    rep(i, n) {
+        for (auto [j, ind] : graph[i]) {
+            if (rem[ind]) {
+                act[g[i]].push_back(g[j]);
+                act[g[j]].push_back(g[i]);
+            }
+        }
+    }
+
+    repv(i, act) {
+        sortv(i);
+        i.erase(unique(all(i)), i.end());
+    }
+
+    ll ans = (ll)n * (n - 1) / 2;
+    function<ll(int, int)> calc = [&](int i, int p) {
+        ll count = c[i];
+        repv(j, act[i]) {
+            if (j == p) {
+                continue;
+            }
+
+            ll tm = calc(j, i);
+            rmin(ans, tm * (tm - 1) / 2 + (n - tm) * (n - tm - 1) / 2);
+            count += tm;
+        }
+        return count;
+    };
+
+    calc(0, 0);
+    cout << ans << '\n';
+}
+
+int main()
+{
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    pre();
+
+    int t;
+    (TEST && cin >> t) || (t = 1);
+    while (t--) {
+        solve();
+    }
+}