'commit'

TangDou/Topic/HuanGenDp/POJ3585.cpp

@@ -3,55 +3,55 @@
 #include <vector>
 #include <cstring>
 using namespace std;
-const int N = 2e5 + 10;
+const int N = 2e5 + 10, M = N << 1;
+
 int T, n, du[N];
 
-struct node {
+// 链式前向星
-    int to, w;
+int e[M], h[N], idx, w[M], ne[M];
-};
+void add(int a, int b, int c = 0) {
-vector<node> c[N];
+    e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
+}
 
-bool v[N];
 int d[N], f[N];
 
 void clean() {
-    memset(v, 0, sizeof v);
+    // 初始化链式前向星
+    memset(h, -1, sizeof h);
+    idx = 0;
+
     memset(du, 0, sizeof du);
     memset(d, 0, sizeof d);
     memset(f, 0, sizeof f);
-
-    for (int i = 1; i <= n; i++) c[i].clear();
 }
-void dp(int x) {
+void dp(int u, int fa) {
-    v[x] = 1;
+    for (int i = h[u]; ~i; i = ne[i]) {
-    int size = c[x].size() - 1;
+        int v = e[i];
-    for (int i = 0; i <= size; i++) {
+        if (v == fa) continue;
-        int to = c[x][i].to, w = c[x][i].w;
+        dp(v, u);
-        if (v[to]) continue;
+        if (du[v] == 1)
-        dp(to);
+            d[u] += w[i];
-        if (du[to] == 1)
-            d[x] += w;
         else
-            d[x] += min(d[to], w);
+            d[u] += min(d[v], w[i]);
     }
     return;
 }
-void dfs(int x) {
+void dfs(int u, int fa) {
-    v[x] = 1;
+    for (int i = h[u]; ~i; i = ne[i]) {
-    int size = c[x].size() - 1;
+        int v = e[i];
-    for (int i = 0; i <= size; i++) {
+        if (v == fa) continue;
-        int to = c[x][i].to, w = c[x][i].w;
+        if (du[u] == 1)
-        if (v[to]) continue;
+            f[v] = d[v] + w[i];
-        if (du[x] == 1)
-            f[to] = d[to] + w;
         else
-            f[to] = d[to] + min(f[x] - min(d[to], w), w);
+            f[v] = d[v] + min(f[u] - min(d[v], w[i]), w[i]);
-        dfs(to);
+        dfs(v, u);
     }
     return;
 }
 
 int main() {
+    // 加快读入
+    ios::sync_with_stdio(false), cin.tie(0);
     cin >> T;
     while (T--) {
         cin >> n;
@@ -59,15 +59,13 @@ int main() {
         int x, y, z;
         for (int i = 1; i < n; i++) {
             cin >> x >> y >> z;
-            c[x].push_back((node){y, z});
+            add(x, y, z), add(y, x, z);
-            c[y].push_back((node){x, z});
+            du[x]++, du[y]++;
-            du[x]++;
-            du[y]++;
         }
-        dp(1);
+        dp(1, 0);
         f[1] = d[1];
-        memset(v, 0, sizeof v);
+
-        dfs(1);
+        dfs(1, 0);
         int ans = 0;
         for (int i = 1; i <= n; i++) ans = max(ans, f[i]);
         printf("%d\n", ans);