'commit'

TangDou/Topic/HuanGenDp/P6419.cpp

@@ -2,33 +2,39 @@
 using namespace std;
 const int N = 500010, M = N << 1;
 #define int long long
+
+// 链式前向星
+int e[M], h[N], idx, w[M], ne[M];
+void add(int a, int b, int c = 0) {
+    e[idx] = b, ne[idx] = h[a], w[idx] = c, h[a] = idx++;
+}
+
 int n, m, k;
-#define INF 1e18
+
 int sz[N]; // 以u为根节点是否有人
 int g[N];  // 从u出发把u子树上的人都送回家再回到u所需要的时间
-vector<pair<int, int>> vec[N];
+
-int max1[N]; // u的子树中最长链的长度
+int mx1[N]; // u的子树中最长链的长度
-int max2[N]; // u的子树中次长链
+int mx2[N]; // u的子树中次长链
 int up[N];  // 不在u的子树内，距离u最远的那个人的家到u的距离
 int id[N];  // 最长链条是哪条链
 int ans[N]; // 从u出发把所有点都送回家再回到u的结果
 
-// ans[i] -max(up[i],max1[i]);
+// ans[i] -max(up[i],mx1[i]);
 void dfs1(int u, int fa) {
-    for (auto ts : vec[u]) {
+    for (int i = h[u]; ~i; i = ne[i]) {
-        int v = ts.first;
+        int v = e[i];
-        int w = ts.second;
         if (v == fa) continue;
         dfs1(v, u);
         if (sz[v]) {
-            g[u] += g[v] + 2 * w;
+            g[u] += g[v] + 2 * w[i];
-            int now = max1[v] + w;
+            int now = mx1[v] + w[i];
-            if (now >= max1[u]) {
+            if (now >= mx1[u]) {
-                max2[u] = max1[u];
+                mx2[u] = mx1[u];
-                max1[u] = now;
+                mx1[u] = now;
                 id[u] = v;
-            } else if (now >= max2[u]) {
+            } else if (now >= mx2[u]) {
-                max2[u] = now;
+                mx2[u] = now;
             }
         }
         sz[u] += sz[v];
@@ -36,22 +42,21 @@ void dfs1(int u, int fa) {
 }
 
 void dfs2(int u, int fa) {
-    for (auto ts : vec[u]) {
+    for (int i = h[u]; ~i; i = ne[i]) {
-        int v = ts.first;
+        int v = e[i];
-        int w = ts.second;
         if (v == fa) continue;
         if (sz[v] == k) {
             ans[v] = g[v];
             up[v] = 0;
         } else if (sz[v] == 0) {
-            ans[v] = ans[u] + 2 * w;
+            ans[v] = ans[u] + 2 * w[i];
-            up[v] = max(up[u], max1[u]) + w;
+            up[v] = max(up[u], mx1[u]) + w[i];
         } else if (sz[v] && sz[v] != k) {
             ans[v] = ans[u];
             if (id[u] == v) {
-                up[v] = max(max2[u], up[u]) + w;
+                up[v] = max(mx2[u], up[u]) + w[i];
             } else
-                up[v] = max(up[u], max1[u]) + w;
+                up[v] = max(up[u], mx1[u]) + w[i];
         }
 
         dfs2(v, u);
@@ -59,21 +64,26 @@ void dfs2(int u, int fa) {
 }
 
 signed main() {
-    cin >> n >> k;
+    // 初始化链式前向星
-    for (int i = 1; i < n; i++) {
+    memset(h, -1, sizeof h);
+
+    cin >> n >> k;                // n个节点,要接k个人
+    for (int i = 1; i < n; i++) { // n-1条边
         int a, b, c;
         cin >> a >> b >> c;
-        vec[a].push_back({b, c});
+        add(a, b, c), add(b, a, c);
-        vec[b].push_back({a, c});
     }
+
     for (int i = 1; i <= k; i++) {
         int x;
         cin >> x;
-        sz[x] = 1;
+        sz[x] = 1; // x节点有一个人
     }
+    // 第一次dfs
     dfs1(1, 0);
     ans[1] = g[1];
+    // 第二次dfs
     dfs2(1, 0);
-    int minn = INF;
+
-    for (int u = 1; u <= n; u++) cout << ans[u] - max(up[u], max1[u]) << endl;
+    for (int u = 1; u <= n; u++) cout << ans[u] - max(up[u], mx1[u]) << endl;
 }