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
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
| #include <bits/stdc++.h>
#define x first
#define y second
#define y1 Y1
#define y2 Y2
#define mp make_pair
#define pb push_back
using namespace std;
typedef long long LL;
typedef pair<int, int> pii;
template <typename T> inline int Chkmax (T &a, T b) { return a < b ? a = b, 1 : 0; }
template <typename T> inline int Chkmin (T &a, T b) { return a > b ? a = b, 1 : 0; }
inline void proc_status()
{
ifstream t ("/proc/self/status");
cerr << string (istreambuf_iterator <char> (t), istreambuf_iterator <char> ()) <<endl;
}
inline int read ()
{
int sum = 0, fl = 1; char ch = getchar();
for (; !isdigit(ch); ch = getchar()) if (ch == '-') fl = -1;
for (; isdigit(ch); ch = getchar()) sum = (sum << 3) + (sum << 1) + ch - '0';
return sum * fl;
}
const int Maxn = 50000 + 100;
int N, M;
int e, Begin[Maxn], To[Maxn << 1], Next[Maxn << 1], W[Maxn << 1];
int A[Maxn], r_sum;
int dep[Maxn], anc[22][Maxn];
inline void add_edge (int x, int y, int z) { To[++e] = y; Next[e] = Begin[x]; Begin[x] = e; W[e] = z; }
inline void dfs_pre (int x, int f)
{
for (int i = 1; i <= 20; ++i) anc[i][x] = anc[i - 1][anc[i - 1][x]];
for (int i = Begin[x]; i; i = Next[i])
{
int y = To[i];
if (y == f) continue;
anc[0][y] = x;
dep[y] = dep[x] + W[i];
dfs_pre (y, x);
}
}
vector <pii> Rest, Left;
int Vis[Maxn];
inline void dfs (int x, int f)
{
if (Vis[x]) return ;
int tmp = 1, fl = 0;
for (int i = Begin[x]; i; i = Next[i])
{
int y = To[i];
if (y == f) continue;
fl = 1;
dfs(y, x);
tmp &= Vis[y];
}
if (fl) Vis[x] = tmp;
}
inline int Check (int now_ans)
{
Rest.clear(), Left.clear();
for (int i = 1; i <= N; ++i) Vis[i] = 0;
for (int i = 1; i <= M; ++i)
{
int tmp = A[i];
if (now_ans < dep[tmp])
{
int x = tmp, now = now_ans;
for (int j = 20; j >= 0; --j)
{
int fa = anc[j][x];
if (fa && dep[x] - dep[fa] <= now)
{
now -= dep[x] - dep[fa];
x = fa;
}
}
Vis[x] = 1;
}
}
dfs(1, 0);
for (int i = 1; i <= M; ++i)
{
int tmp = A[i];
if (now_ans >= dep[tmp])
{
int x = tmp;
for (int j = 20; j >= 0; --j) if (anc[j][x] > 1) x = anc[j][x];
Rest.pb(mp(now_ans - dep[tmp], x));
}
}
for (int i = Begin[1]; i; i = Next[i])
{
int x = To[i];
if (!Vis[x]) Left.pb(mp(W[i], x));
}
sort(Rest.begin(), Rest.end());
sort(Left.begin(), Left.end());
int j = 0;
if (!Left.size()) return 1;
for (int i = 0; i < Rest.size(); ++i)
{
if (!Vis[Rest[i].y]) Vis[Rest[i].y] = 1;
else if (Rest[i].x >= Left[j].x) Vis[Left[j].y] = 1;
while (j < Left.size() && Vis[Left[j].y]) ++j;
}
return j >= Left.size();
}
inline void Solve ()
{
dfs_pre(1, 0);
int l = 0, r = r_sum, ans = -1;
while (l <= r)
{
int mid = l + r >> 1;
if (Check(mid)) r = mid - 1, ans = mid;
else l = mid + 1;
}
cout<<ans<<endl;
}
inline void Input ()
{
N = read();
for (int i = 1; i < N; ++i)
{
int x = read(), y = read(), z = read();
add_edge (x, y, z);
add_edge (y, x, z);
r_sum += z;
}
M = read();
for (int i = 1; i <= M; ++i) A[i] = read();
}
int main()
{
#ifndef ONLINE_JUDGE
freopen("blockade.in", "r", stdin);
freopen("blockade.out", "w", stdout);
#endif
Input();
Solve();
return 0;
}
|