HDU 5016 Mart Master II (树上点分治)

#include <iostream>
#include <string.h>
#include <math.h>
#include <queue>
#include <algorithm>
#include <stdlib.h>
#include <map>
#include <set>
#include <stdio.h>
#include <time.h>
using namespace std;
#define LL __int64
#define pi acos(-1.0)
#pragma comment(linker, "/STACK:1024000000")
const int mod=1e9+7;
const int INF=0x3f3f3f3f;
const double eqs=1e-9;
const int MAXN=100000+10;
int head[MAXN], cnt, root, min1, tot;
int siz[MAXN], vis[MAXN], d[MAXN], id[MAXN], ans[MAXN], dis[MAXN];
int color[MAXN];
struct node
{
int v, w, next;
}edge[MAXN<<1];
void add(int u, int v, int w)
{
edge[cnt].v=v;
edge[cnt].w=w;
edge[cnt].next=head[u];
head[u]=cnt++;
}
struct N
{
int dis, id;
}F[MAXN];
bool cmp(N x, N y)
{
return x.dis<y.dis||(x.dis==y.dis&&x.id<y.id);
}
void init()
{
memset(head,-1,sizeof(head));
memset(vis,0,sizeof(vis));
memset(d,INF,sizeof(d));
memset(id,0,sizeof(id));
memset(ans,0,sizeof(ans));
cnt=0;
}
void dfs1(int u, int fa)
{
if(color[u]){
id[u]=u;
d[u]=0;
}
for(int i=head[u];i!=-1;i=edge[i].next){
int v=edge[i].v;
if(v==fa) continue ;
dfs1(v,u);
if(d[u]>d[v]+edge[i].w){
d[u]=d[v]+edge[i].w;
id[u]=id[v];
}
else if(d[u]==d[v]+edge[i].w)
id[u]=min(id[u],id[v]);
}
}
void dfs2(int u, int fa)
{
for(int i=head[u];i!=-1;i=edge[i].next){
int v=edge[i].v;
if(v==fa) continue ;
if(d[v]>d[u]+edge[i].w){
d[v]=d[u]+edge[i].w;
id[v]=id[u];
}
else if(d[v]==d[u]+edge[i].w){
id[v]=min(id[v],id[u]);
}
dfs2(v,u);
}
}
void getsize(int u, int fa)
{
siz[u]=1;
for(int i=head[u];i!=-1;i=edge[i].next){
int v=edge[i].v;
if(v==fa||vis[v]) continue ;
getsize(v,u);
siz[u]+=siz[v];
}
}
void getroot(int u, int fa, int s)
{
int max1=0;
for(int i=head[u];i!=-1;i=edge[i].next){
int v=edge[i].v;
if(v==fa||vis[v]) continue ;
getroot(v,u,s);
max1=max(max1,siz[v]);
}
max1=max(max1,s-siz[u]);
if(min1>max1){
min1=max1;
root=u;
}
}
void getdis(int u, int fa, int l)
{
dis[u]=l;
F[tot].dis=d[u]-l;
F[tot++].id=id[u];
for(int i=head[u];i!=-1;i=edge[i].next){
int v=edge[i].v;
if(v==fa||vis[v]) continue ;
getdis(v,u,l+edge[i].w);
}
}
int BS(int l, int u)
{
int low=0, high=tot-1, mid, ans=-1;
while(low<=high){
mid=low+high>>1;
if(F[mid].dis<l||(F[mid].dis==l&&F[mid].id<=u)){
low=mid+1;
ans=mid;
}
else high=mid-1;
}
return ans+1;
}
void getans(int u, int fa, int f, int s)
{
int tmp=BS(dis[u],u);
ans[u]+=f*(s-tmp);
for(int i=head[u];i!=-1;i=edge[i].next){
int v=edge[i].v;
if(v==fa||vis[v]) continue ;
getans(v,u,f,s);
}
}
void Cal(int u, int l, int f)
{
tot=0;
getdis(u,-1,l);
sort(F,F+tot,cmp);
getans(u,-1,f,siz[u]);
}
void work(int u)
{
vis[u]=1;
getsize(u,-1);
Cal(u,0,1);
for(int i=head[u];i!=-1;i=edge[i].next){
int v=edge[i].v;
if(vis[v]) continue ;
Cal(v,edge[i].w,-1);
min1=INF;
getroot(v,u,siz[v]);
work(root);
}
}
int main()
{
int n, u, v, w, i, res;
while(scanf("%d",&n)!=EOF){
init();
for(i=1;i<n;i++){
scanf("%d%d%d",&u,&v,&w);
add(u,v,w);
add(v,u,w);
}
for(i=1;i<=n;i++){
scanf("%d",&color[i]);
}
dfs1(1,-1);
dfs2(1,-1);
min1=INF;
getsize(1,-1);
getroot(1,-1,n);
work(root);
res=0;
for(i=1;i<=n;i++){
if(color[i]) continue ;
res=max(res,ans[i]);
}
printf("%d\n",res);
}
return 0;
}