#1698. 【2022.10.27 联考】传送

https://sjzezoj.com/submission/62433

S2OJ/1698/1698.cpp

@@ -0,0 +1,70 @@
+#include <iostream>
+#include <algorithm>
+#include <vector>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e6 + 5;
+
+int t, n, m, q, cnt, block[N], color[N];
+std::vector<int> g[N];
+bool flag[N];
+
+void dfs(int u, int f) {
+    block[u] = cnt;
+
+    for (int v : g[u]) {
+        if (color[v] != -1 && color[u] == color[v]) {
+            flag[cnt] = true;
+        } else if (color[v] == -1) {
+            color[v] = color[u] ^ 1;
+            dfs(v, u);
+        }
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> t >> n >> m;
+
+    for (int i = 1, u, v; i <= m; i++) {
+        cin >> u >> v;
+
+        g[u].emplace_back(v);
+        g[v].emplace_back(u);
+    }
+
+    std::fill_n(color, N, -1);
+
+    for (int i = 1; i <= n; i++) {
+        if (color[i] == -1) {
+            cnt++;
+            color[i] = 0;
+            dfs(i, 0);
+        }
+    }
+
+    cin >> q;
+
+    while (q--) {
+        int s, t;
+
+        cin >> s >> t;
+
+        if (s == t) {
+            cout << 0 << endl;
+        } else if (block[s] != block[t]) {
+            cout << -1 << endl;
+        } else if (flag[block[s]] || color[s] != color[t]) {
+            cout << 1 << endl;
+        } else {
+            cout << 2 << endl;
+        }
+    }
+
+    return 0;
+}