SPOJ 375 树链剖分

思路：
链剖裸题……

//By SiriusRen
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define N 22222
char ch[11];
int n,cases,root,tree[N*4],xx,yy,ans;
int tot,first[N],next[N],v[N],w[N];
int cnt,top[N],deep[N],size[N],son[N],rec[N],f[N];
struct Edge{int from,to,weight;}edge[N];
void add(int x,int y,int z){
    w[tot]=z,v[tot]=y;
    next[tot]=first[x],first[x]=tot++;
}
void dfs(int x,int fa){
    size[x]=1;son[x]=0;
    for(int i=first[x];~i;i=next[i]){
        if(v[i]==fa)continue;
        f[v[i]]=x;
        deep[v[i]]=deep[x]+1;
        dfs(v[i],x);
        size[x]+=size[v[i]];
        if(size[v[i]]>size[son[x]])son[x]=v[i];
    }
}
void dfs2(int x,int fa,int tp){
    rec[x]=++cnt;top[x]=tp;
    if(son[x])dfs2(son[x],x,tp);
    for(int i=first[x];~i;i=next[i])
        if(v[i]!=son[x]&&v[i]!=fa)dfs2(v[i],x,v[i]);
}
void insert(int l,int r,int pos){
    if(l==r){tree[pos]=yy;return;}
    int mid=(l+r)>>1;
    if(mid<xx)insert(mid+1,r,pos<<1|1);
    else insert(l,mid,pos<<1);
    tree[pos]=max(tree[pos<<1],tree[pos<<1|1]);
}
int query(int l,int r,int pos,int Left,int Right){
    if(l>=Left&&r<=Right)return tree[pos];
    int mid=(l+r)>>1;
    if(mid<Left)return query(mid+1,r,pos<<1|1,Left,Right);
    else if(mid>=Right)return query(l,mid,pos<<1,Left,Right);
    else return max(query(l,mid,pos<<1,Left,Right),query(mid+1,r,pos<<1|1,Left,Right));
}
void find(){
    int fx=top[xx],fy=top[yy];
    while(fx!=fy){
        if(deep[fx]<deep[fy])swap(xx,yy),swap(fx,fy);
        ans=max(ans,query(1,n,1,rec[fx],rec[xx]));
        xx=f[fx];fx=top[xx];
    }
    if(xx==yy)return;
    if(deep[xx]>deep[yy])swap(xx,yy);
    ans=max(ans,query(1,n,1,rec[son[xx]],rec[yy]));
}
int main(){
    scanf("%d",&cases);
    while(cases--){
        memset(tree,0,sizeof(tree));
        memset(size,0,sizeof(size));
        memset(first,-1,sizeof(first));
        scanf("%d",&n);
        for(int i=1;i<n;i++){
            scanf("%d%d%d",&edge[i].from,&edge[i].to,&edge[i].weight);
            add(edge[i].from,edge[i].to,edge[i].weight);
            add(edge[i].to,edge[i].from,edge[i].weight);
        }
        root=(n+1)>>1;
        f[root]=deep[root]=cnt=tot=0;
        dfs(root,root),dfs2(root,root,root);
        for(int i=1;i<n;i++){
            if(deep[edge[i].from]>deep[edge[i].to])swap(edge[i].from,edge[i].to);
            xx=rec[edge[i].to],yy=edge[i].weight;
            insert(1,cnt,1);
        }
        while(scanf("%s",ch)&&ch[0]!='D'){
            scanf("%d%d",&xx,&yy);
            if(ch[0]=='Q')ans=0,find(),printf("%d
",ans);
            else xx=rec[edge[xx].to],insert(1,n,1);
        }
    }
}