poj3237 Tree

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;

const int Max=10086,Inf=(1<<30);

inline int MIN(int a,int b)
{
	return a<b?a:b;
}

inline int MAX(int a,int b)
{
	return a>b?a:b;
}

int val[Max];

struct SegmentTree
{
	int maxv[Max<<2],minv[Max<<2];
	bool flag[Max<<2];

	inline void PushUp(int idx)
	{
		maxv[idx]=MAX(maxv[idx<<1],maxv[idx<<1|1]);
		minv[idx]=MIN(minv[idx<<1],minv[idx<<1|1]);
	}

	inline void PushDown(int idx)
	{
		if(flag[idx])
		{
			int l=idx<<1,r=l+1;
			maxv[l]=-maxv[l],minv[l]=-minv[l],swap(maxv[l],minv[l]);
			maxv[r]=-maxv[r],minv[r]=-minv[r],swap(maxv[r],minv[r]);
			flag[l]^=1,flag[r]^=1;
			flag[idx]=false;
		}
	}

	void Build(int idx,int left,int right)
	{
		flag[idx]=false;
		if(left==right)
		{
			maxv[idx]=minv[idx]=val[left];
			return;
		}
		int mid=(left+right)>>1;
		Build(idx<<1,left,mid);
		Build(idx<<1|1,mid+1,right);
		PushUp(idx);
	}

	void Update(int idx,int left,int right,int pos,int data)
	{
		if(left==right)
		{
			maxv[idx]=minv[idx]=data;
			return;
		}
		PushDown(idx);
		int mid=(left+right)>>1;
		if(pos<=mid) Update(idx<<1,left,mid,pos,data);
		else Update(idx<<1|1,mid+1,right,pos,data);
		PushUp(idx);
	}

	void Negate(int idx,int left,int right,int L,int R)
	{
		if(L<=left && right<=R)
		{
			maxv[idx]=-maxv[idx],minv[idx]=-minv[idx];
			swap(maxv[idx],minv[idx]);
			flag[idx]^=1;
			return;
		}
		PushDown(idx);
		int mid=(left+right)>>1;
		if(L<=mid) Negate(idx<<1,left,mid,L,R);
		if(mid<R) Negate(idx<<1|1,mid+1,right,L,R);
		PushUp(idx);
	}

	int Query(int idx,int left,int right,int L,int R)
	{
		if(L<=left && right<=R)
			return maxv[idx];
		PushDown(idx);
		int mid=(left+right)>>1,ans=-Inf;
		if(L<=mid) ans=MAX(ans,Query(idx<<1,left,mid,L,R));
		if(mid<R) ans=MAX(ans,Query(idx<<1|1,mid+1,right,L,R));
		return ans;
	}
}tree;

int f[Max],fa[Max],tot[Max],son[Max],top[Max],pos[Max],depth[Max],size;

struct Edge
{
	int v,w,next;
}edge[Max<<1];

void Add(int u,int v,int w,int& cnt)
{
	edge[cnt].v=v;
	edge[cnt].w=w;
	edge[cnt].next=f[u];
	f[u]=cnt++;

	edge[cnt].v=u;
	edge[cnt].w=w;
	edge[cnt].next=f[v];
	f[v]=cnt++;
}

void Init()
{
	memset(f,-1,sizeof(f));
	top[1]=fa[1]=1,size=depth[1]=0;
}

void Dfs1(int cur)
{
	tot[cur]=1,son[cur]=0;
	int v,maxv=-1;
	for(int i=f[cur];i!=-1;i=edge[i].next)
	{
		v=edge[i].v;
		if(v!=fa[cur])
		{
			fa[v]=cur,depth[v]=depth[cur]+1;
			Dfs1(v);
			tot[cur]+=tot[v];
			if(tot[v]>maxv) maxv=tot[v],son[cur]=v;
		}
	}
}

void Dfs2(int cur)
{
	int v=son[cur],i;
	pos[cur]=++size;
	if(v) top[v]=top[cur],Dfs2(v);
	for(i=f[cur];i!=-1;i=edge[i].next)
	{
		v=edge[i].v;
		if(v==fa[cur]) val[pos[cur]]=edge[i].w;
		else if(v!=son[cur]) top[v]=v,Dfs2(v);
	}
}

inline void Update(int idx,int data)
{
	int i=idx*2-1;
	int u=edge[i].v,v=edge[i^1].v;
	if(depth[u]<depth[v]) swap(u,v);
	tree.Update(1,2,size,pos[u],data);
}

void Negate(int u,int v)
{
	int topu=top[u];
	int topv=top[v];
	while(topu!=topv)
	{
		if(depth[topu]<depth[topv]) swap(u,v),swap(topu,topv);
		tree.Negate(1,2,size,pos[topu],pos[u]);
		u=fa[topu],topu=top[u];
	}
	if(u==v) return ;
	if(depth[u]>depth[v]) swap(u,v);
	tree.Negate(1,2,size,pos[son[u]],pos[v]);
}

int Query(int u,int v)
{
	if(u==v) return 0;
	int topu=top[u];
	int topv=top[v];
	int ans=-Inf;
	while(topu!=topv)
	{
		if(depth[topu]<depth[topv]) swap(u,v),swap(topu,topv);
		ans=MAX(ans,tree.Query(1,2,size,pos[topu],pos[u]));
		u=fa[topu],topu=top[u];
	}
	if(u==v) return ans;
	if(depth[u]>depth[v]) swap(u,v);
	ans=MAX(ans,tree.Query(1,2,size,pos[son[u]],pos[v]));
	return ans;
}

int main()
{
	//freopen("test.txt","r",stdin);
	int N,T,u,v,cnt,i,w;
	char str[22];
	cin>>T;
	while(T--)
	{
		scanf("%d",&N);
		Init();
		for(i=1,cnt=0;i<N;++i)
		{
			scanf("%d %d %d",&u,&v,&w);
			Add(u,v,w,cnt);
		}
		Dfs1(1),Dfs2(1),tree.Build(1,2,N);
		while(scanf("%s",str),str[0]!='D')
		{
			scanf("%d %d",&u,&v);
			if(str[0]=='C') Update(u,v);
			else if(str[0]=='N') Negate(u,v);
			else printf("%d\n",Query(u,v));
		}
	}
	return 0;
}