From a2b5c850ee11299df65b6068f2897145fa09b19a Mon Sep 17 00:00:00 2001
From: Baoshuo <i@baoshuo.ren>
Date: Sun, 25 Sep 2022 16:10:47 +0800
Subject: [PATCH] F - Well-defined Path Queries on a Namori

https://atcoder.jp/contests/abc266/submissions/35157689
---
 AtCoder/ABC266/F/F.cpp | 95 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 AtCoder/ABC266/F/F.cpp

diff --git a/AtCoder/ABC266/F/F.cpp b/AtCoder/ABC266/F/F.cpp
new file mode 100644
index 00000000..6546e761
--- /dev/null
+++ b/AtCoder/ABC266/F/F.cpp
@@ -0,0 +1,95 @@
+#include <iostream>
+#include <numeric>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 2e5 + 5;
+
+int n, q, cnt, fa[N], color[N], root;
+std::vector<int> g[N], circle;
+
+int find(int x) {
+    return fa[x] == x ? x : fa[x] = find(fa[x]);
+}
+
+bool dfs1(int u, int f) {
+    if (f != 0 && u == root) {
+        return true;
+    }
+
+    for (int v : g[u]) {
+        if (v == f) continue;
+
+        if (dfs1(v, u)) {
+            circle.emplace_back(u);
+
+            return true;
+        }
+    }
+
+    return false;
+}
+
+void dfs2(int u, int f, int c) {
+    color[u] = c;
+
+    for (int v : g[u]) {
+        if (color[v]) continue;
+
+        dfs2(v, u, c);
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    std::iota(fa + 1, fa + 1 + n, 1);
+
+    for (int i = 1, u, v; i <= n; i++) {
+        cin >> u >> v;
+
+        g[u].emplace_back(v);
+        g[v].emplace_back(u);
+
+        int x = find(u),
+            y = find(v);
+
+        if (x == y) {
+            root = u;
+        } else {
+            fa[x] = y;
+        }
+    }
+
+    dfs1(root, 0);
+
+    for (int u : circle) {
+        color[u] = ++cnt;
+    }
+
+    for (int u : circle) {
+        for (int v : g[u]) {
+            if (color[v]) continue;
+
+            dfs2(v, u, color[u]);
+        }
+    }
+
+    cin >> q;
+
+    while (q--) {
+        int x, y;
+
+        cin >> x >> y;
+
+        cout << (color[x] == color[y] ? "Yes" : "No") << endl;
+    }
+
+    return 0;
+}