bzoj 2435 dfs超级大水题

OnlineJudges/lydsy/2435.cpp

@@ -0,0 +1,40 @@
+#include <cstdio>
+typedef long long int64;
+const int maxn = 1000010;
+int head[maxn], to[maxn << 1], next[maxn << 1], ecnt, sz[maxn], u[maxn], v[maxn], w[maxn];
+inline void addEdge(int f, int t)
+{
+    ecnt++;
+    next[ecnt] = head[f];
+    head[f] = ecnt;
+    to[ecnt] = t;
+}
+inline int min(int x, int y) { return x < y ? x : y; }
+inline int64 abs(int64 x) { return x >= 0 ? x : -x; }
+void dfs(int x, int f)
+{
+    sz[x] = 1;
+    for (int cur = head[x]; cur; cur = next[cur])
+        if (to[cur] != f)
+        {
+            dfs(to[cur], x);
+            sz[x] += sz[to[cur]];
+        }
+}
+int main()
+{
+    int n;
+    scanf("%d", &n);
+    for (int i = 1; i < n; i++)
+    {
+        scanf("%d%d%d", u + i, v + i, w + i);
+        addEdge(u[i], v[i]);
+        addEdge(v[i], u[i]);
+    }
+    dfs(1, 0);
+    int64 ans = 0;
+    for (int i = 1; i < n; i++)
+        ans += abs(n - (min(sz[u[i]], sz[v[i]]) << 1)) * w[i];
+    printf("%lld", ans);
+    return 0;
+}