'commit'

TangDou/CSP-J/J2_2019/4_1.cpp

@@ -0,0 +1,53 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+typedef pair<int, int> PII;
+#define x first
+#define y second
+
+const int N = 1e5 + 10, M = N << 1;
+
+// 20个测试点，过了7个，得了35分,其它TLE
+// 邻接表
+int e[M], h[N], idx, ne[M];
+void add(int a, int b) {
+    e[idx] = b, ne[idx] = h[a], h[a] = idx++;
+}
+bool bfs(int start, int dist) {
+    queue<PII> q;
+    q.push({start, dist});
+
+    while (q.size()) {
+        auto u = q.front();
+        q.pop();
+
+        if (u.x == 1 && u.y == 0) return true; // 在用完所有步数后，到达1号点，成功！
+
+        for (int i = h[u.x]; ~i; i = ne[i]) {
+            int v = e[i];
+            if (u.y) q.push({v, u.y - 1});
+        }
+    }
+    return false;
+}
+
+int main() {
+    // 链式前向星
+    memset(h, -1, sizeof h);
+
+    int n, m, Q;
+    cin >> n >> m >> Q;
+
+    while (m--) {
+        int a, b;
+        cin >> a >> b;
+        add(a, b), add(b, a); // 无向图，双向建边
+    }
+
+    while (Q--) {
+        int u, dist;
+        cin >> u >> dist;
+        cout << (bfs(u, dist) ? "Yes" : "No") << endl;
+    }
+    return 0;
+}