题目大意
有一棵树，(n)((nleq2*10^5))个点，每条边(i)有颜色(w_i)，共有(m)((mleq n))种颜色，第(i)种颜色的权值是(c_i)((|c_i|leq10^4))
定义一条路径的权值是该路径上所有同色段的颜色的权值之和
给定(l,r)，求边数在([l,r])中权值最大的路径的权值
题解
将每个点的所有边按颜色排序后，对这棵树进行点分治，每次统计过当前重心的路径
用线段树统计应该挺板的吧
有人用单调队列做，然而我不会，先坑着
代码
#include<algorithm>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<iomanip>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<vector>
#define rep(i,x,y) for(register int i=(x);i<=(y);++i)
#define dwn(i,x,y) for(register int i=(x);i>=(y);--i)
#define pii pair<int ,int>
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define maxn 200010
#define inf 2147483647
#define ls (u<<1)
#define rs (u<<1|1)
#define mi (L+R>>1)
#define vv(x) v[x][i].se
using namespace std;
int read()
{
int x=0,f=1;char ch=getchar();
while(!isdigit(ch)&&ch!='-')ch=getchar();
if(ch=='-')f=-1,ch=getchar();
while(isdigit(ch))x=(x<<1)+(x<<3)+ch-'0',ch=getchar();
return x*f;
}
void write(int x)
{
if(x==0){putchar('0'),putchar('
');return;}
int f=0;char ch[20];
if(x<0)putchar('-'),x=-x;
while(x)ch[++f]=x%10+'0',x/=10;
while(f)putchar(ch[f--]);
putchar('
');
return;
}
int n,m,l,r,ans=-inf,wt,sumsiz,mnsz,vis[maxn];
long long cnt;
int siz[maxn],c[maxn];
vector<pii >v[maxn];
struct tree
{
int tr[maxn<<2],mk[maxn<<2];
void pu(int u){tr[u]=max(tr[ls],tr[rs]);}
void mark(int u,int k){mk[u]=tr[u]=k;}
void pd(int u){if(mk[u]){mark(ls,mk[u]),mark(rs,mk[u]),mk[u]=0;}}
void add(int u,int L,int R,int x,int k)
{
if(x<=L&&R<=x){tr[u]=max(k,tr[u]),mk[u]=0;return;}
pd(u);
if(x<=mi)add(ls,L,mi,x,k);
else add(rs,mi+1,R,x,k);
return pu(u);
}
int ask(int u,int L,int R,int x,int y)
{
if(y<L||R<x)return -inf;
if(x<=L&&R<=y)return tr[u];
pd(u);
int res=-inf;
if(x<=mi)res=ask(ls,L,mi,x,y);
if(y>mi)res=max(res,ask(rs,mi+1,R,x,y));
return res;
}
}t[2];
void getwt(int u,int fa)
{
siz[u]=1;int nwmx=0,lim=v[u].size();
rep(i,0,lim-1)if(vv(u)!=fa&&!vis[vv(u)])getwt(vv(u),u),siz[u]+=siz[vv(u)],nwmx=max(nwmx,siz[vv(u)]);
nwmx=max(nwmx,sumsiz-siz[u]);
if(nwmx<mnsz)wt=u,mnsz=nwmx;
return;
}
void asktr(int u,int fa,int fac,int dep,int num)
{
if(dep>r)return;
int lim=v[u].size(),tmp=max(t[0].ask(1,0,n,l-dep,r-dep),t[1].ask(1,0,n,l-dep,r-dep));if(tmp!=-inf)ans=max(ans,tmp+num);
rep(i,0,lim-1)if(!vis[vv(u)]&&vv(u)!=fa)asktr(vv(u),u,v[u][i].fi,dep+1,num+(v[u][i].fi==fac?0:c[v[u][i].fi]));
}
void addtr(int u,int fa,int fac,int dep,int num,int f)
{
if(dep>r)return;
int lim=v[u].size();t[f].add(1,0,n,dep,num);
rep(i,0,lim-1)if(!vis[vv(u)]&&vv(u)!=fa)addtr(vv(u),u,v[u][i].fi,dep+1,num+(v[u][i].fi==fac?0:c[v[u][i].fi]),f);
}
void getans(int u,int nowsiz)
{
sumsiz=nowsiz,mnsz=n+1,getwt(u,0);int now=wt;
int lim=v[now].size(),p=0;t[0].mark(1,-inf),t[1].mark(1,-inf);t[0].add(1,0,n,0,0);
cnt+=(long long)nowsiz;
rep(i,0,lim-1)
{
if(!vis[vv(now)])
{
asktr(vv(now),now,v[now][i].fi,1,c[v[now][i].fi]),
addtr(vv(now),now,v[now][i].fi,1,0,1);
}
if(i!=lim-1&&v[now][i].fi!=v[now][i+1].fi)
{
rep(j,p,i)if(!vis[v[now][j].se])addtr(v[now][j].se,now,v[now][j].fi,1,c[v[now][j].fi],0);
t[1].mark(1,-inf);
p=i+1;
}
}
vis[now]=1;
rep(i,0,lim-1)if(!vis[vv(now)])getans(vv(now),siz[vv(now)]>siz[now]?nowsiz-siz[now]:siz[vv(now)]);
return;
}
int main()
{
n=read(),m=read(),l=read(),r=read();if(l<=0&&0<=r)ans=0;
rep(i,1,m)c[i]=read();
rep(i,1,n-1){int x=read(),y=read(),z=read();v[x].pb(mp(z,y)),v[y].pb(mp(z,x));}
rep(i,1,n)sort(v[i].begin(),v[i].end());
getans(1,n);
write(ans);
return 0;
}
/*
5 3 1 4
-1 -5 -2
1 2 1
1 3 1
2 4 2
2 5 3
*/
/*
8 4 3 4
-7 9 6 1
1 2 1
1 3 2
1 4 1
2 5 1
5 6 2
3 7 1
3 8 3
*/