From e4e338fdbff3d92c86abf0152011271471690032 Mon Sep 17 00:00:00 2001
From: Baoshuo <i@baoshuo.ren>
Date: Mon, 12 Sep 2022 21:37:01 +0800
Subject: [PATCH] =?UTF-8?q?1987=20-=20=E5=B0=8F=E4=B8=91=E7=AB=9F=E5=9C=A8?=
 =?UTF-8?q?=E6=88=91=E8=BA=AB=E8=BE=B9?=
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77475
---
 bjtu/1987/1987.cpp | 48 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 bjtu/1987/1987.cpp

diff --git a/bjtu/1987/1987.cpp b/bjtu/1987/1987.cpp
new file mode 100644
index 00000000..89d392ce
--- /dev/null
+++ b/bjtu/1987/1987.cpp
@@ -0,0 +1,48 @@
+#include <iostream>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e4 + 5;
+
+int n, m, cnt, cnt2;
+std::vector<int> g[N];
+bool vis[N], flag = true;
+
+void dfs(int u) {
+    cnt++;
+    vis[u] = true;
+
+    for (int v : g[u]) {
+        if (!vis[v]) dfs(v);
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n >> m;
+
+    for (int i = 1, u, v; i <= m; i++) {
+        cin >> u >> v;
+
+        g[u].emplace_back(v);
+        g[v].emplace_back(u);
+    }
+
+    for (int i = 1; i <= n; i++) {
+        if (!vis[i]) {
+            int pre = cnt;
+            dfs(i);
+
+            if (cnt - pre > 1) cnt2++;
+        }
+    }
+
+    cout << (cnt2 <= 1 ? "YES" : "NO") << endl;
+
+    return 0;
+}