LOJ #6145. 「2017 山东三轮集训 Day7」Easy 点分树+线段树

这个就比较简单了~

Code:

#include <cstdio>
#include <algorithm>
#define N 100004
#define inf 1000000000
#define setIO(s) freopen(s".in","r",stdin)  //    , freopen(s".out","w",stdout)
using namespace std;
int n,edges;
int hd[N],to[N<<1],nex[N<<1],val[N<<1];
void add(int u,int v,int c)
{
	nex[++edges]=hd[u],hd[u]=edges,to[edges]=v,val[edges]=c;
}
namespace tree
{
	int size[N],son[N],dep[N],dis[N],fa[N],top[N];
	void dfs1(int u,int ff)
	{
		size[u]=1,fa[u]=ff;
		for(int i=hd[u];i;i=nex[i])
			if(to[i]!=ff)
			{
				dis[to[i]]=dis[u]+val[i],dep[to[i]]=dep[u]+1;
				dfs1(to[i],u),size[u]+=size[to[i]];
				if(size[to[i]]>size[son[u]]) son[u]=to[i];
			}
	}
	void dfs2(int u,int tp)
	{
		top[u]=tp;
		if(son[u]) dfs2(son[u],tp);
		for(int i=hd[u];i;i=nex[i])
			if(to[i]!=fa[u]&&to[i]!=son[u])
				dfs2(to[i],to[i]);
	}
	int LCA(int x,int y)
	{
		while(top[x]!=top[y])
			dep[top[x]]>dep[top[y]]?x=fa[top[x]]:y=fa[top[y]];
		return dep[x]<dep[y]?x:y;
	}
	int Dis(int x,int y)
	{
		return dis[x]+dis[y]-(dis[LCA(x,y)]<<1);
	}
};
namespace seg
{
	int tot;
	#define lson t[x].ls
	#define rson t[x].rs
	struct Node
	{
		int ls,rs,min;
	}t[N*100];
	int newnode()
	{
		t[++tot].min=inf;
		return tot;
	}
	void pushup(int x)
	{
		t[x].min=inf;
		if(lson) t[x].min=min(t[x].min,t[lson].min);
		if(rson) t[x].min=min(t[x].min,t[rson].min);
	}
	void update(int &x,int l,int r,int p,int v)
	{
		if(!x) x=newnode();
		if(l==r)
		{
			t[x].min=min(t[x].min,v);
			return;
		}
		int mid=(l+r)>>1;
		if(p<=mid) update(lson,l,mid,p,v);
		else update(rson,mid+1,r,p,v);
		pushup(x);
	}
	int query(int x,int l,int r,int L,int R)
	{
		if(!x) return inf;
		if(l>=L&&r<=R) return t[x].min;
		int mid=(l+r)>>1,re=inf;
		if(L<=mid) re=min(re,query(lson,l,mid,L,R));
		if(R>mid)  re=min(re,query(rson,mid+1,r,L,R));
		return re;
	}
	#undef lson
	#undef rson
};
int root,sn;
int size[N],Fa[N],mx[N],vis[N],rt[N];
void getroot(int u,int ff)
{
	size[u]=1,mx[u]=0;
	for(int i=hd[u];i;i=nex[i])
		if(to[i]!=ff&&!vis[to[i]])
			getroot(to[i],u),size[u]+=size[to[i]],mx[u]=max(mx[u],size[to[i]]);
	mx[u]=max(mx[u],sn-mx[u]);
	if(mx[u]<mx[root]) root=u;
}
void dfs(int u,int ff)
{
	size[u]=1;
	for(int i=hd[u];i;i=nex[i])
		if(to[i]!=ff&&!vis[to[i]])
			dfs(to[i],u),size[u]+=size[to[i]];
}
void calc(int u,int ff,int dep,int tp)
{
	seg::update(rt[tp],1,n,u,dep);
	for(int i=hd[u];i;i=nex[i])
		if(to[i]!=ff&&!vis[to[i]])
			calc(to[i],u,dep+val[i],tp);
}
void prepare(int u)
{
	vis[u]=1,calc(u,0,0,u);
	for(int i=hd[u];i;i=nex[i])
		if(!vis[to[i]])
			dfs(to[i],u),root=0,sn=size[to[i]],getroot(to[i],u),Fa[root]=u,prepare(root);
}
int query(int u,int l,int r)
{
	int re=seg::query(rt[u],1,n,l,r),U=u;
	for(;Fa[u];u=Fa[u])
		re=min(re, seg::query(rt[Fa[u]],1,n,l,r)+tree::Dis(U,Fa[u]));
	return re;
}
int main()
{
	int i,j,m;
	// setIO("input");
	scanf("%d",&n);
	for(i=1;i<n;++i)
	{
		int a,b,c;
		scanf("%d%d%d",&a,&b,&c),add(a,b,c),add(b,a,c);
	}
	tree::dfs1(1,0),tree::dfs2(1,1);
	root=0,mx[root]=sn=n,getroot(1,0),prepare(root);
	scanf("%d",&m);
	for(i=1;i<=m;++i)
	{
		int l,r,x;
		scanf("%d%d%d",&l,&r,&x);
		printf("%d\n",query(x,l,r));
	}
	return 0;
}