1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
| #include <iostream>
#include <cstdio>
#include <cstring>
#define maxn 100010
#define INF 1000000000000000000ll
#define ll long long
using namespace std;
int n, a[maxn], sum;
struct Edge {
int to, next, w;
} e[maxn * 2]; int c1, head[maxn];
inline void add_edge(int u, int v, int w) {
e[c1].to = v; e[c1].w = w;
e[c1].next = head[u]; head[u] = c1++;
}
int sz[maxn]; ll g[maxn], f[maxn];
void dfs(int u, int fa) {
sz[u] = a[u];
for (int i = head[u]; ~i; i = e[i].next) {
int v = e[i].to, w = e[i].w; if (v == fa) continue;
dfs(v, u); sz[u] += sz[v]; f[u] += f[v] + 1ll * sz[v] * w;
}
}
ll ans = INF;
void Dfs(int u, int fa) {
ans = min(ans, g[u]);
for (int i = head[u]; ~i; i = e[i].next) {
int v = e[i].to, w = e[i].w; if (v == fa) continue;
ll res = g[u] - 1ll * w * sz[v] - f[v] + 1ll * (sum - sz[v]) * w;
g[v] = res + f[v]; Dfs(v, u);
}
}
int main() { memset(head, -1, sizeof head);
scanf("%d", &n);
for (int i = 1; i <= n; ++i) scanf("%d", &a[i]), sum += a[i];
for (int i = 1; i < n; ++i) {
int x, y, z; scanf("%d%d%d", &x, &y, &z);
add_edge(x, y, z); add_edge(y, x, z);
} dfs(1, 0); g[1] = f[1]; Dfs(1, 0);
cout << ans << endl;
return 0;
}
|