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| #include <bits/stdc++.h>
#define R register
#define ll long long
#define sum(a, b, mod) ((a + b) % mod)
const int MaxN = 5e5 + 10;
struct edge
{
double d;
int next, to;
};
edge e[MaxN << 1];
int n, cnt;
int head[MaxN];
double p[MaxN], f[MaxN], g[MaxN], h[u];
inline void add_edge(int u, int v, double d)
{
++cnt;
e[cnt].to = v;
e[cnt].d = d;
e[cnt].next = head[u];
head[u] = cnt;
}
inline void dfs(int u, int fa)
{
f[u] = 1 - p[u];
for (int i = head[u]; i; i = e[i].next)
{
int v = e[i].to;
if (v == fa)
continue;
dfs(v, u), f[u] *= (1 - e[i].d + (e[i].d * f[v]));
}
}
inline void dfs1(int u, int fa, int id)
{
if (u == 1)
g[u] = f[u];
else
{
h[u] = g[fa] / (1 - e[id].d + e[id].d * f[u]);
g[u] = f[u] * (1 - e[id].d + e[id].d * h[u]);
}
for (int i = head[u]; i; i = e[i].next)
{
int v = e[i].to;
if (v == fa)
continue;
dfs1(v, u, i);
}
}
int main()
{
scanf("%d", &n);
for (int i = 1; i < n; i++)
{
int u, v;
double d;
scanf("%d%d%lf", &u, &v, &d), d *= 0.01;
add_edge(u, v, d), add_edge(v, u, d);
}
for (int i = 1; i <= n; i++)
scanf("%lf", &p[i]), p[i] *= 0.01;
dfs(1, 0), dfs1(1, 0, 0);
double ans = 0;
for (int i = 1; i <= n; i++)
ans += 1.00 - g[i];
printf("%.6lf", ans);
return 0;
}
|