'commit'

TangDou/AcWing/Test/TD.cpp

@@ -0,0 +1,85 @@
+#include <bits/stdc++.h>
+using namespace std;
+const int N = 100010, M = 200010;
+int depth[N], f[N][25];
+int n, m;
+int d[N];
+int ans;
+const int T = 17;
+
+int e[M], h[N], idx, ne[M];
+void add(int a, int b) {
+    e[idx] = b, ne[idx] = h[a], h[a] = idx++;
+}
+int start = 1;
+
+void bfs() {
+    queue<int> q;
+    q.push(start);
+    depth[start] = 1;
+    while (q.size()) {
+        int u = q.front();
+        q.pop();
+        for (int i = h[u]; ~i; i = ne[i]) {
+            int v = e[i];
+            if (!depth[v]) {
+                depth[v] = depth[u] + 1;
+                q.push(v);
+                f[v][0] = u;
+                for (int k = 1; k <= T; k++) f[v][k] = f[f[v][k - 1]][k - 1];
+            }
+        }
+    }
+}
+
+int lca(int a, int b) {
+    if (depth[a] < depth[b]) swap(a, b);
+    for (int i = T; i >= 0; i--)
+        if (depth[f[a][i]] >= depth[b]) a = f[a][i];
+    if (a == b) return a;
+    for (int i = T; i >= 0; i--)
+        if (f[a][i] != f[b][i])
+            a = f[a][i], b = f[b][i];
+    return f[a][0];
+}
+
+void dfs(int u, int fa) {
+    for (int i = h[u]; ~i; i = ne[i]) {
+        int v = e[i];
+        if (v == fa) continue;
+        dfs(v, u);
+        d[u] += d[v];
+    }
+}
+
+int main() {
+    int a, b;
+    scanf("%d %d", &n, &m);
+    memset(h, -1, sizeof h);
+    for (int i = 1; i < n; i++) {
+        scanf("%d %d", &a, &b);
+        add(a, b), add(b, a);
+    }
+
+    bfs();
+
+    for (int i = 0; i < m; i++) {
+        scanf("%d %d", &a, &b);
+
+        d[a]++, d[b]++;
+        int p = lca(a, b);
+
+        d[p] -= 2;
+    }
+
+    dfs(start, 0);
+
+    for (int i = 1; i <= n; i++) {
+        if (i == start) continue;
+        if (d[i] == 0) ans += m;
+        if (d[i] == 1) ans += 1;
+    }
+
+    printf("%d\n", ans);
+    return 0;
+}