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OI-codes/BZOJ/1827/1827.cpp

82 lines
1.3 KiB
C++

#include <iostream>
#include <vector>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 1e5 + 5;
int n, sum, root, c[N], siz[N], max_siz[N], dep[N];
long long ans;
std::vector<std::pair<int, int>> g[N];
void dfs1(int u, int f) {
siz[u] = c[u];
for (auto e : g[u]) {
int v = e.first,
w = e.second;
if (v == f) continue;
dfs1(v, u);
siz[u] += siz[v];
max_siz[u] = std::max(max_siz[u], siz[v]);
}
max_siz[u] = std::max(max_siz[u], sum - siz[u]);
}
void dfs2(int u, int f) {
for (auto e : g[u]) {
int v = e.first,
w = e.second;
if (v == f) continue;
dep[v] = dep[u] + w;
dfs2(v, u);
}
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> c[i];
sum += c[i];
}
for (int i = 1, u, v, w; i <= n; i++) {
cin >> u >> v >> w;
g[u].emplace_back(v, w);
g[v].emplace_back(u, w);
}
dfs1(1, 0);
for (int i = 1; i <= n; i++) {
if (!root || max_siz[i] < max_siz[root]) {
root = i;
}
}
dep[0] = -1;
dfs2(root, 0);
for (int i = 1; i <= n; i++) {
ans += static_cast<long long>(c[i]) * dep[i];
}
cout << ans << endl;
return 0;
}