显而易见地，点分治然后暴力维护两棵线段树（颜色相同 / 不同）算贡献，算完之后合并这两棵线段树再看下一种颜色（
代码： 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
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
using namespace std;
const int N = 2e5;
int n,m,l,r;
int a[N + 5],v[N + 5];
int to[(N << 1) + 5],pre[(N << 1) + 5],val[(N << 1) + 5],first[N + 5];
inline void add(int u,int v,int w)
{
static int tot = 0;
to[++tot] = v,val[tot] = w,pre[tot] = first[u],first[u] = tot;
}
namespace SEG
{
struct node
{
int max;
int ls,rs;
} seg[(N << 3) + 10];
int rt[N + 5];
int init()
{
seg[0].max = -2e9;
return 0;
}
int Init = init(),tot;
void insert(int x,int k,int &p,int tl,int tr)
{
!p && (seg[p = ++tot].max = -2e9,seg[p].ls = seg[p].rs = 0),seg[p].max = max(seg[p].max,k);
if(tl == tr)
return ;
int mid = tl + tr >> 1;
x <= mid ? insert(x,k,seg[p].ls,tl,mid) : insert(x,k,seg[p].rs,mid + 1,tr);
}
int query(int l,int r,int p,int tl,int tr)
{
if(!p || (l <= tl && tr <= r))
return seg[p].max;
int mid = tl + tr >> 1;
int ret = -2e9;
l <= mid && (ret = max(ret,query(l,r,seg[p].ls,tl,mid)));
r > mid && (ret = max(ret,query(l,r,seg[p].rs,mid + 1,tr)));
return ret;
}
int merge(int p,int q)
{
if(!p || !q)
return p | q;
seg[p].max = max(seg[p].max,seg[q].max),
seg[p].ls = merge(seg[p].ls,seg[q].ls),seg[p].rs = merge(seg[p].rs,seg[q].rs);
return p;
}
}
namespace LIS
{
int pre[N + 5],first[N + 5];
inline void add(int p,int v)
{
pre[p] = first[v],first[v] = p;
}
}
int vis[N + 5],sum,sz[N + 5],max_part[N + 5],cur[N + 5],rt;
int done[N + 5];
int dis[N + 5],dep[N + 5],fa[N + 5];
int col[N + 5],len;
int ans;
void get_rt(int p)
{
done[p] = fa[p] = 0;
for(int flag;;)
{
flag = 0;
if(!done[p])
sz[p] = 1,max_part[p] = 0,cur[p] = first[p],done[p] = 1;
for(register int i = cur[p];i;i = pre[i])
{
cur[p] = pre[i];
if((to[i] ^ fa[p]) && !vis[to[i]])
{
done[to[i]] = 0,fa[to[i]] = p,p = to[i],flag = 1;
break;
}
}
if(!flag)
{
max_part[p] = max(max_part[p],sum - sz[p]);
max_part[p] < max_part[rt] && (rt = p);
if(fa[p])
{
sz[fa[p]] += sz[p],max_part[fa[p]] = max(max_part[fa[p]],sz[p]);
p = fa[p];
}
else
break;
}
}
/*sz[p] = 1,max_part[p] = 0;
for(register int i = first[p];i;i = pre[i])
if((to[i] ^ fa) && !vis[to[i]])
get_rt(to[i],p),sz[p] += sz[to[i]],max_part[p] = max(max_part[p],sz[to[i]]);
max_part[p] = max(max_part[p],sum - sz[p]);
max_part[p] < max_part[rt] && (rt = p);*/
}
void get_dis(int p)
{
done[p] = fa[p] = 0;
for(int flag;;)
{
flag = 0;
if(!done[p])
cur[p] = first[p],done[p] = 1;
for(register int i = cur[p];i;i = pre[i])
{
cur[p] = pre[i];
if((to[i] ^ fa[p]) && !vis[to[i]])
{
done[to[i]] = 0,fa[to[i]] = p,dep[to[i]] = dep[p] + 1,v[to[i]] = val[i],dis[to[i]] = dis[p] + (v[p] != v[to[i]]) * a[v[to[i]]],p = to[i],flag = 1;
break;
}
}
if(!flag)
if(fa[p])
p = fa[p];
else
break;
}
/*for(register int i = first[p];i;i = pre[i])
if((to[i] ^ fa) && !vis[to[i]])
dep[to[i]] = dep[p] + 1,v[to[i]] = val[i],dis[to[i]] = dis[p] + (v[p] != v[to[i]]) * a[v[to[i]]],get_dis(to[i],p);*/
}
void calc(int p,int c)
{
done[p] = fa[p] = 0;
for(int flag;;)
{
flag = 0;
if(!done[p])
{
cur[p] = first[p],done[p] = 1;
if(dep[p] >= l && dep[p] <= r)
ans = max(ans,dis[p]);
int temp = SEG::query(max(l - dep[p],1),r - dep[p],SEG::rt[0],1,n);
if(temp > -2e9)
ans = max(ans,temp + dis[p]);
temp = SEG::query(max(l - dep[p],1),r - dep[p],SEG::rt[c],1,n);
if(temp > -2e9)
ans = max(ans,temp + dis[p] - a[c]);
}
for(register int i = cur[p];i;i = pre[i])
{
cur[p] = pre[i];
if((to[i] ^ fa[p]) && !vis[to[i]] && dep[to[i]] <= r)
{
done[to[i]] = 0,fa[to[i]] = p,p = to[i],flag = 1;
break;
}
}
if(!flag)
if(fa[p])
p = fa[p];
else
break;
}
/*if(dep[p] >= l && dep[p] <= r)
ans = max(ans,dis[p]);
if(dep[p] > r)
return ;
for(register int i = first[p];i;i = pre[i])
if((to[i] ^ fa) && !vis[to[i]])
calc(to[i],p,c);*/
}
void insert(int p,int c)
{
done[p] = fa[p] = 0;
for(int flag;;)
{
flag = 0;
if(!done[p])
{
cur[p] = first[p],done[p] = 1;
SEG::insert(dep[p],dis[p],SEG::rt[c],1,n);
}
for(register int i = cur[p];i;i = pre[i])
{
cur[p] = pre[i];
if((to[i] ^ fa[p]) && !vis[to[i]] && dep[to[i]] <= r)
{
done[to[i]] = 0,fa[to[i]] = p,p = to[i],flag = 1;
break;
}
}
if(!flag)
if(fa[p])
p = fa[p];
else
break;
}
/*if(dep[p] > r)
return ;
SEG::insert(dep[p],dis[p],SEG::rt[c],1,n);
for(register int i = first[p];i;i = pre[i])
if((to[i] ^ fa) && !vis[to[i]])
insert(to[i],p,c);*/
}
void solve(int p)
{
vis[p] = 1,dep[p] = dis[p] = v[p] = 0,get_dis(p),len = 0;
for(register int i = first[p];i;i = pre[i])
if(!vis[to[i]])
LIS::add(to[i],v[to[i]]),col[++len] = v[to[i]];
sort(col + 1,col + len + 1),len = unique(col + 1,col + len + 1) - col - 1;
for(register int ci = 1,c;ci <= len;++ci)
{
c = col[ci];
for(register int i = LIS::first[c];i;i = LIS::pre[i])
calc(i,c),insert(i,c);
SEG::rt[0] = SEG::merge(SEG::rt[0],SEG::rt[c]),
LIS::first[c] = SEG::rt[c] = 0;
}
SEG::tot = SEG::rt[0] = 0;
for(register int i = first[p];i;i = pre[i])
if(!vis[to[i]])
rt = 0,sum = sz[to[i]],fa[to[i]] = p,get_rt(to[i]),solve(rt);
}
int main()
{
max_part[0] = 0x3f3f3f3f,ans = -2e9;
scanf("%d%d%d%d",&n,&m,&l,&r);
for(register int i = 1;i <= m;++i)
scanf("%d",a + i);
int u,v,w;
for(register int i = 2;i <= n;++i)
scanf("%d%d%d",&u,&v,&w),add(u,v,w),add(v,u,w);
vis[0] = 1,rt = 0,sum = n,get_rt(1),solve(rt);
printf("%d\n",ans);
}