[USACO09OPEN]Hide and Seek S

R57850314

Luogu/problem/P2951/P2951.cpp

@@ -0,0 +1,44 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, m, u, v, dist[200005], ans1, ans2, ans3;
+vector<int> g[200005];
+
+void spfa() {
+    memset(dist, 0x3f, sizeof(dist));
+    dist[1] = 0;
+    queue<int> q;
+    q.push(1);
+    while (!q.empty()) {
+        auto t = q.front();
+        q.pop();
+        for (auto i : g[t]) {
+            if (dist[i] > dist[t] + 1) {
+                dist[i] = dist[t] + 1;
+                q.push(i);
+            }
+        }
+    }
+}
+
+int main() {
+    cin >> n >> m;
+    for (int i = 0; i < m; i++) {
+        cin >> u >> v;
+        g[u].push_back(v);
+        g[v].push_back(u);
+    }
+    spfa();
+    for (int i = 1; i <= n; i++) {
+        if (ans2 < dist[i]) {
+            ans2 = dist[i];
+            ans1 = i;
+        }
+    }
+    for (int i = 1; i <= n; i++) {
+        ans3 += dist[i] == ans2;
+    }
+    cout << ans1 << ' ' << ans2 << ' ' << ans3 << endl;
+    return 0;
+}