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| #include <cstdio>
#include <algorithm>
using namespace std;
typedef long long LL;
const int N = 1e6 + 10, M = 2e6 + 10;
int n;
LL f[N], C[N], d[N], sz[N], wt[M];
int idx, hd[N], nxt[M], edg[M];
void dfs1(int x)
{
sz[x] = C[x];
for (int i = hd[x]; ~i; i = nxt[i])
if (!d[edg[i]] && edg[i] != 1)
{
d[edg[i]] = d[x] + wt[i];
dfs1(edg[i]);
sz[x] += sz[edg[i]];
}
}
void dfs2(int x)
{
for (int i = hd[x]; ~i; i = nxt[i])
if (!f[edg[i]])
{
f[edg[i]] = f[x] + wt[i] * (sz[1] - sz[edg[i]]) - wt[i] * sz[edg[i]];
dfs2(edg[i]);
}
}
void add(int a, int b, int c)
{
nxt[++idx] = hd[a];
hd[a] = idx;
edg[idx] = b;
wt[idx] = c;
}
int main()
{
scanf("%d", &n);
for (int i = 1; i <= n; i++)
hd[i] = -1;
for (int i = 1; i <= n; i++)
scanf("%lld", &C[i]);
for (int i = 1, a, b, c; i < n; i++)
{
scanf("%d%d%d", &a, &b, &c);
add(a, b, c);
add(b, a, c);
}
d[1] = 0;
dfs1(1);
for (int i = 1; i <= n; i++)
f[1] += d[i] * C[i];
dfs2(1);
LL mn = f[1];
for (int i = 2; i <= n; i++)
mn = min(mn, f[i]);
printf("%lld", mn);
return 0;
}
|