SPOJ QTREE 树链剖分

#include <cstdio>
#include <cstring>
#include <iostream>
#include <set>
#include <queue>
#include <algorithm>
#include <cmath>
#include <vector>
using namespace std;
#define N 10010
#define ls o<<1
#define rs o<<1|1
#define define_m int m=(l+r)>>1
int maxn[N<<2] , dis[N];

struct Edge{
    int x,y,d;
    Edge(int x=0 , int y=0 , int d=0):x(x),y(y),d(d){}
};

vector<Edge> v[N];
int fa[N] , son[N] , sz[N] , top[N] , dep[N] , id[N] , k;
int n , st[N] , en[N] , d[N] , val;
char str[20];

void dfs(int u , int f , int d)
{
    fa[u] = f;
    sz[u] = 1 , dep[u]=d , son[u]=0;
    int len = v[u].size();
    int maxn = 0;
    for(int i=0 ; i<len ; i++){
        int to=v[u][i].y;
        if(to==f) continue;
        dfs(to,u,d+1);
        sz[u]+=sz[to];
        if(sz[to]>maxn){
            son[u]=to;
            maxn = sz[to];
        }
    }
}

void dfs1(int u , int f , int head)
{
    int l=v[u].size();
    top[u] = head;
    if(son[u]){
        id[son[u]] = ++k;
        dfs1(son[u] , u , head);
    }
    for(int i=0 ; i<l ; i++){
        int to = v[u][i].y;
        if(to==f || to==son[u]) continue;
        id[to] = ++k;
        dfs1(to , u , to);
    }
}

void push_up(int o)
{
    maxn[o] = max(maxn[ls] , maxn[rs]);
}

void build(int o , int l , int r)
{
    if(l==r){
        maxn[o] = dis[l];
        return ;
    }
    define_m;
    build(ls , l , m);
    build(rs , m+1 , r);
    push_up(o);
}

void update(int o , int l , int r , int pos, int v)
{
    if(l==r && l==pos){
        maxn[o] = v;
        return;
    }
    define_m;
    if(m>=pos) update(ls , l , m , pos , v);
    else update(rs , m+1 , r , pos , v);
    push_up(o);
}

int query(int o , int l , int r , int s , int t)
{
  //  cout<<"query: "<<o<<" "<<l<<" "<<r<<" "<<s<<" "<<t<<endl;
    if(l>=s && r<=t){
        return maxn[o];
    }
    int ans = 0;
    define_m;
    if(m>=s) ans = max(ans , query(ls , l , m , s , t));
    if(m<t) ans= max(ans , query(rs , m+1 , r , s , t));
    return ans;
}

int CalPath(int u , int v)
{
    int top1=top[u] , top2=top[v];
    int ans = 0;
    while(top1 != top2){
        if(dep[top1]<dep[top2]){
            swap(top1 , top2);
            swap(u , v);
        }
        ans = max(ans , query(1 , 1 , k , id[top1] , id[u]));
        u=fa[top1];
        top1=top[u];
    }
    if(u!=v){
        if(dep[u]<dep[v]){
            swap(u,v);
        }
        ans=max(ans,query(1,1,k,id[son[v]],id[u]));
       // cout<<"in: "<<id[u]<<" "<<id[son[v]]<<endl;
       // cout<<"u: "<<u<<" v: "<<v<<" "<<ans<<endl;
    }
    return ans;
}

int main()
{
   // freopen("a.in" , "r" , stdin);
    int T;
    scanf("%d" , &T);
    while(T--)
    {
        scanf("%d" , &n);
        for(int i=1 ; i<=n ; i++) v[i].clear();
        for(int i=1 ; i<n ; i++){
            scanf("%d%d%d" , &st[i] , &en[i] , &d[i]);
            v[st[i]].push_back(Edge(st[i],en[i],d[i]));
            v[en[i]].push_back(Edge(en[i],st[i],d[i]));
        }
        k=0;
        dfs(1,0,1);
        dfs1(1,0,1);
        for(int i=1 ; i<n ; i++){
            int ID;
            if(st[i] != fa[en[i]]) ID = id[st[i]];
            else ID = id[en[i]];
              //  cout<<"ID: "<<ID<<endl;
            dis[ID] = d[i];
        }
       /* for(int i=1 ; i<=n ; i++){
            cout<<fa[i]<<" "<<son[i]<<" "<<dep[i]<<" "<<sz[i]<<" "<<top[i]<<" "<<id[i]<<endl;
            if(i<n) cout<<"i: "<<dis[i]<<endl;
        }*/
        build(1,1,k);
       // cout<<"sum: "<<sum[1]<<" "<<sum[2]<<" "<<sum[3]<<endl;
        while(scanf("%s" , str) && str[0]!='D'){
            int t1 , t2;
            scanf("%d%d" , &t1 , &t2);
            if(str[0] == 'C'){
                int ID;
                if(st[t1] != fa[en[t1]]) ID = id[st[t1]];
                else ID = id[en[t1]];
              //  cout<<"ID: "<<ID<<endl;
                update(1,1,k,ID,t2);
            }
            else{
                int ans = CalPath(t1,t2);
                printf("%d\n" , ans);
            }
        }
    }
    return 0;
}