From e0e8d0ca8fdd12692ef513d7afd83a8ccf179d12 Mon Sep 17 00:00:00 2001
From: Baoshuo <i@baoshuo.ren>
Date: Tue, 20 Sep 2022 19:21:30 +0800
Subject: [PATCH] P3520 [POI2011] SMI-Garbage

https://www.luogu.com.cn/record/87053341
---
 Luogu/P3520/P3520.cpp | 91 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 Luogu/P3520/P3520.cpp

diff --git a/Luogu/P3520/P3520.cpp b/Luogu/P3520/P3520.cpp
new file mode 100644
index 00000000..b8545982
--- /dev/null
+++ b/Luogu/P3520/P3520.cpp
@@ -0,0 +1,91 @@
+#include <iostream>
+#include <stack>
+#include <utility>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e5 + 5,
+          M = 1e6 + 5;
+
+int n, m, d[N], root;
+bool vis[N], in_stack[N], edge_used[M];
+std::stack<int> st;
+std::vector<std::pair<int, int>> g[N];
+std::vector<std::vector<int>> ans;
+
+void dfs(int u) {
+    vis[u] = true;
+
+    for (auto e : g[u]) {
+        int v = e.first,
+            id = e.second;
+
+        if (edge_used[id]) continue;
+        edge_used[id] = true;
+
+        dfs(v);
+    }
+
+    if (in_stack[u]) {
+        std::vector<int> res{u};
+
+        while (st.top() != u) {
+            res.emplace_back(st.top());
+            in_stack[st.top()] = false;
+            st.pop();
+        }
+
+        res.emplace_back(u);
+        ans.emplace_back(res);
+    } else {
+        st.push(u);
+        in_stack[u] = true;
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    for (int i = 1, a, b, s, t; i <= m; i++) {
+        cin >> a >> b >> s >> t;
+
+        if (s ^ t) {
+            g[a].emplace_back(b, i);
+            g[b].emplace_back(a, i);
+
+            d[a]++, d[b]++;
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        if (d[i] % 2 != 0) {
+            cout << "NIE" << endl;
+
+            exit(0);
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        if (!vis[i]) dfs(i);
+    }
+
+    cout << ans.size() << endl;
+
+    for (auto& item : ans) {
+        cout << item.size() - 1 << ' ';
+
+        for (int& x : item) {
+            cout << x << ' ';
+        }
+
+        cout << endl;
+    }
+
+    return 0;
+}