[POJ2114]Boatherds（点分治+二分）

题目描述

题解

代码

#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<cmath>
using namespace std;
#define N 10005

int n,x,y,m,sum,root;
int q
,ans
;
int tot,point
,nxt[N*2],v[N*2],c[N*2];
int size
,big
,d
,deep
;
bool vis
;

void clear()
{
x=y=m=sum=root=0;
memset(ans,0,sizeof(ans));
tot=0;memset(point,0,sizeof(point));
memset(vis,0,sizeof(vis));
}
void add(int x,int y,int z)
{
++tot; nxt[tot]=point[x]; point[x]=tot; v[tot]=y; c[tot]=z;
}
void getroot(int x,int fa)
{
size[x]=1;big[x]=0;
for (int i=point[x];i;i=nxt[i])
if (v[i]!=fa&&!vis[v[i]])
{
getroot(v[i],x);
size[x]+=size[v[i]];
big[x]=max(big[x],size[v[i]]);
}
big[x]=max(big[x],sum-size[x]);
if (big[x]<big[root]) root=x;
}
void getdeep(int x,int fa)
{
deep[++deep[0]]=d[x];
for (int i=point[x];i;i=nxt[i])
if (v[i]!=fa&&!vis[v[i]])
{
d[v[i]]=d[x]+c[i];
getdeep(v[i],x);
}
}
int findl(int l,int r,int k)
{
int ans=0;
while (l<=r)
{
int mid=(l+r)>>1;
if (deep[mid]==k) ans=mid,r=mid-1;
else if (deep[mid]<k) l=mid+1;
else r=mid-1;
}
return ans;
}
int findr(int l,int r,int k)
{
int ans=-1;
while (l<=r)
{
int mid=(l+r)>>1;
if (deep[mid]==k) ans=mid,l=mid+1;
else if (deep[mid]<k) l=mid+1;
else r=mid-1;
}
return ans;
}
int calc(int x,int now,int k)
{
d[x]=now;deep[0]=0;
getdeep(x,0);
sort(deep+1,deep+deep[0]+1);
int t=0;
for (int i=1;i<=deep[0];++i)
{
if (deep[i]+deep[i]>k) break;
int l=findl(i+1,deep[0],k-deep[i]);
int r=findr(i+1,deep[0],k-deep[i]);
t+=r-l+1;
}
return t;
}
void dfs(int x)
{
for (int i=1;i<=m;++i)
ans[i]+=calc(x,0,q[i]);
vis[x]=1;
for (int i=point[x];i;i=nxt[i])
if (!vis[v[i]])
{
for (int j=1;j<=m;++j)
ans[j]-=calc(v[i],c[i],q[j]);
sum=size[v[i]];root=0;
getroot(v[i],0);
dfs(root);
}
}

int main()
{
while (~scanf("%d",&n))
{
if (!n) break;
clear();
for (int i=1;i<=n;++i)
{
while (~scanf("%d",&x))
{
if (!x) break;
scanf("%d",&y);
add(i,x,y);add(x,i,y);
}
}
while (~scanf("%d",&x))
{
if (!x) break;
q[++m]=x;
}
big[0]=N;
sum=n;root=0;
getroot(1,0);
dfs(root);
for (int i=1;i<=m;++i)
if (ans[i]) puts("AYE");
else puts("NAY");
puts(".");
}
}