From 7bb1be51b5e4c4367eb348cb46098f449c1a3185 Mon Sep 17 00:00:00 2001
From: Baoshuo <i@baoshuo.ren>
Date: Sun, 29 Jan 2023 10:24:53 +0800
Subject: [PATCH] =?UTF-8?q?#1850.=20=E3=80=90Gym104090G=E3=80=91Subgraph?=
 =?UTF-8?q?=20Isomorphism?=
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https://sjzezoj.com/submission/67557
---
 S2OJ/1818/1818.cpp | 106 +++++++++++++++++++++++++++++++++++++
 S2OJ/1850/1850.cpp | 128 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 234 insertions(+)
 create mode 100644 S2OJ/1818/1818.cpp
 create mode 100644 S2OJ/1850/1850.cpp

diff --git a/S2OJ/1818/1818.cpp b/S2OJ/1818/1818.cpp
new file mode 100644
index 00000000..20a7fe2d
--- /dev/null
+++ b/S2OJ/1818/1818.cpp
@@ -0,0 +1,106 @@
+#include <iostream>
+#include <queue>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 2e6 + 5;
+const int INF = 0x3f3f3f3f;
+
+int n, q, t, cnt = 1, pos = 1, lst,
+             a[N], dep[N], fa[N][std::__lg(N) + 1];
+std::vector<int> g[N];
+
+void bfs(int s) {
+    std::fill_n(dep, N, INF);
+
+    std::queue<int> q;
+
+    q.emplace(s);
+    dep[0] = 0;
+    dep[s] = 1;
+
+    while (!q.empty()) {
+        int u = q.front();
+        q.pop();
+
+        for (int v : g[u]) {
+            if (dep[v] > dep[u] + 1) {
+                dep[v] = dep[u] + 1;
+                q.emplace(v);
+                fa[v][0] = u;
+
+                for (int k = 1; k <= std::__lg(n); k++) {
+                    fa[v][k] = fa[fa[v][k - 1]][k - 1];
+                }
+            }
+        }
+    }
+}
+
+int lca(int x, int y) {
+    if (dep[x] < dep[y]) std::swap(x, y);
+
+    for (int k = std::__lg(n); k >= 0; k--) {
+        if (dep[fa[x][k]] >= dep[y]) {
+            x = fa[x][k];
+        }
+    }
+
+    if (x == y) return x;
+
+    for (int k = std::__lg(n); k >= 0; k--) {
+        if (fa[x][k] != fa[y][k]) {
+            x = fa[x][k];
+            y = fa[y][k];
+        }
+    }
+
+    return fa[x][0];
+}
+
+constexpr int get(int x) {
+    return x * (x - 1) / 2;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> q >> t;
+
+    for (int i = 1; i <= n; i++) {
+        cin >> a[i];
+    }
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = i * (i - 1) / 2 + 1; j <= i * (i - 1) / 2 + i; j++) {
+            if (a[pos] == j) {
+                g[j].emplace_back(++cnt);
+                g[j].emplace_back(++cnt);
+
+                pos++;
+            } else {
+                g[j].emplace_back(++cnt);
+            }
+        }
+    }
+
+    bfs(1);
+
+    while (q--) {
+        int x, y;
+
+        cin >> x >> y;
+
+        x = (x - 1 + t * lst) % ((n + 1) * (n + 2) / 2) + 1;
+        y = (y - 1 + t * lst) % ((n + 1) * (n + 2) / 2) + 1;
+
+        cout << (lst = lca(x, y)) << endl;
+    }
+
+    return 0;
+}
+
diff --git a/S2OJ/1850/1850.cpp b/S2OJ/1850/1850.cpp
new file mode 100644
index 00000000..c742fbbb
--- /dev/null
+++ b/S2OJ/1850/1850.cpp
@@ -0,0 +1,128 @@
+#include <iostream>
+#include <functional>
+#include <stack>
+#include <unordered_set>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+// 树哈希
+// https://peehs-moorhsum.blog.uoj.ac/blog/7891
+
+unsigned long long h(unsigned long long x) {
+    return x * x * x * 1237123 + 19260817;
+}
+
+unsigned long long f(unsigned long long x) {
+    return h(x & ((1ull << 31) - 1)) + h(x >> 31);
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    int t;
+
+    cin >> t;
+
+    while (t--) {
+        int n, m;
+
+        cin >> n >> m;
+
+        std::vector<std::vector<int>> g(n + 1);
+
+        for (int i = 1, x, y; i <= m; i++) {
+            cin >> x >> y;
+
+            g[x].emplace_back(y);
+            g[y].emplace_back(x);
+        }
+
+        if (m > n) {
+            cout << "NO" << endl;
+
+            continue;
+        }
+
+        if (m < n) {
+            cout << "YES" << endl;
+
+            continue;
+        }
+
+        // assert(n == m);
+
+        std::stack<int> st;
+        std::vector<int> circle;
+        std::vector<bool> vis1(n + 1);
+
+        std::function<void(int, int)> dfs1 = [&](int u, int f) -> void {
+            if (vis1[u]) {
+                if (circle.empty()) {
+                    while (!st.empty() && st.top() != u) {
+                        circle.emplace_back(st.top());
+                        st.pop();
+                    }
+
+                    circle.emplace_back(u);
+                }
+
+                return;
+            }
+
+            vis1[u] = true;
+            st.emplace(u);
+
+            for (int v : g[u]) {
+                if (v == f) continue;
+
+                dfs1(v, u);
+            }
+
+            if (!st.empty()) st.pop();
+        };
+
+        dfs1(1, 0);
+
+        std::vector<bool> vis2(n + 1);
+        std::vector<unsigned long long> hash(n + 1);
+        std::unordered_set<unsigned long long> set;
+
+        for (int x : circle) vis2[x] = true;
+
+        std::function<void(int)> dfs2 = [&](int u) -> void {
+            vis2[u] = true;
+            hash[u] = 1;
+
+            for (int v : g[u]) {
+                if (vis2[v]) continue;
+
+                dfs2(v);
+
+                hash[u] += f(hash[v]);
+            }
+        };
+
+        for (int x : circle) {
+            dfs2(x);
+            set.emplace(hash[x]);
+        }
+
+        bool flag = circle.size() % 2 == 0;
+
+        for (int i = 0; i + 2 < circle.size(); i++) {
+            if (hash[circle[i]] != hash[circle[i + 2]]) {
+                flag = false;
+
+                break;
+            }
+        }
+
+        cout << (set.size() == 1 || flag ? "YES" : "NO") << endl;
+    }
+
+    return 0;
+}