P5663 [CSP-J2019] 加工零件

R54732144

Luogu/problem/P5663/P5663.cpp

@@ -0,0 +1,40 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, m, q, u, v, a, l, dist[100005][2];
+vector<pair<int, int>> g[100005];
+bool flag;
+
+void bfs() {
+    memset(dist, 0x3f, sizeof(dist));
+    dist[1][0] = 0;
+    queue<pair<int, int>> q;
+    q.push(make_pair(1, 0));
+    while (!q.empty()) {
+        auto t = q.front();
+        q.pop();
+        for (auto i : g[t.first]) {
+            if (dist[i.first][t.second ^ 1] == 0x3f3f3f3f) {
+                dist[i.first][t.second ^ 1] = dist[t.first][t.second] + 1;
+                q.push(make_pair(i.first, t.second ^ 1));
+            }
+        }
+    }
+}
+
+int main() {
+    cin >> n >> m >> q;
+    for (int i = 1; i <= m; i++) {
+        cin >> u >> v;
+        g[u].push_back(make_pair(v, 1));
+        g[v].push_back(make_pair(u, 1));
+        flag = flag || u == 1 || v == 1;
+    }
+    bfs();
+    for (int i = 1; i <= q; i++) {
+        cin >> a >> l;
+        cout << (flag && l >= dist[a][l & 1] ? "Yes" : "No") << endl;
+    }
+    return 0;
+}