BZOJ 1036 [ZJOI2008]树的统计Count

树链剖分挺好的练手题，直接放代码吧。

/**************************************************************
    Problem: 1036
    User: vermouth
    Language: C++
    Result: Accepted
    Time:2756 ms
    Memory:152744 kb
****************************************************************/
 
#include<cstdio>
#include<iostream>
#include<vector>
using namespace std;
const int maxn=2011010;
vector<int> f[maxn];
int val[maxn],dep[maxn],siz[maxn],son[maxn],id[maxn],top[maxn],fa[maxn];
int x,y,cnt;
int T_sum[maxn<<2],T_max[maxn<<2],dfth[maxn];
int query_sum(int rt,int l,int r,int x,int y)
{
    if(x<=l&&y>=r)
    {
        return T_sum[rt];
    }
    int mid=(l+r)>>1;
    if(y<=mid) return query_sum(rt<<1,l,mid,x,y);
    if(x>mid) return query_sum(rt<<1|1,mid+1,r,x,y);
    return query_sum(rt<<1,l,mid,x,y)+query_sum(rt<<1|1,mid+1,r,x,y);
}
 
int query_max(int rt,int l,int r,int x,int y)
{
    if(x<=l&&y>=r)
    {
        return T_max[rt];
    }
    int mid=(l+r)>>1;
    if(y<=mid) return query_max(rt<<1,l,mid,x,y);
    if(x>mid) return query_max(rt<<1|1,mid+1,r,x,y);
    return max(query_max(rt<<1,l,mid,x,y),query_max(rt<<1|1,mid+1,r,x,y));
}
void dfs1(int u,int deep,int fath)
{
    dep[u]=deep;
    siz[u]=1;
    fa[u]=fath;
    for(int i=0;i<f[u].size();i++)
    {
        int v=f[u][i];
        if(v==fath) continue;
        dfs1(v,deep+1,u);
        siz[u]+=siz[v];
        if(siz[son[u]]<siz[v]) son[u]=v;
    }
}
void dfs2(int u,int tp)
{
    top[u]=tp;
    id[u]=++cnt;
    dfth[cnt]=u;
    if(son[u]) dfs2(son[u],tp);
    for(int i=0;i<f[u].size();i++)
    {
        int v=f[u][i];
        if(v==fa[u]||v==son[u]) continue;
        dfs2(v,v);
    }
}
int get_sum(int u,int v)
{
    int sum=0;
    int x=top[u],y=top[v];
    while(x!=y)
    {
        if(dep[x]<dep[y])
        {
            swap(u,v);swap(x,y);
        }
        sum+=query_sum(1,1,cnt,id[x],id[u]);
        u=fa[x];x=top[u];
    }
    if(dep[u]>dep[v]) swap(u,v);
    return sum+query_sum(1,1,cnt,id[u],id[v]);
}   
int get_max(int u,int v)
{
    int ans=-200000000;
    int x=top[u],y=top[v];
    while(x!=y)
    {
        if(dep[x]<dep[y])
        {
            swap(u,v);swap(x,y);
        }
        ans=max(ans,query_max(1,1,cnt,id[x],id[u]));
        u=fa[x];x=top[u];
    }
    if(dep[u]>dep[v]) swap(u,v);
    return max(ans,query_max(1,1,cnt,id[u],id[v]));
}
void build(int rt,int l,int r)
{
    if(l==r)
    {
        T_max[rt]=T_sum[rt]=val[dfth[l]];
        return;
    }
    int mid=(l+r)>>1;
    build(rt<<1,l,mid);
    build(rt<<1|1,mid+1,r);
    T_max[rt]=max(T_max[rt<<1],T_max[rt<<1|1]);
    T_sum[rt]=T_sum[rt<<1]+T_sum[rt<<1|1];
}
 
void query_change(int rt,int l,int r,int x,int val)
{
    if(l==r)
    {
        T_max[rt]=T_sum[rt]=val;
        return;
    }
    int mid=(l+r)>>1;
    if(x<=mid) query_change(rt<<1,l,mid,x,val);
    else query_change(rt<<1|1,mid+1,r,x,val);
    T_max[rt]=max(T_max[rt<<1],T_max[rt<<1|1]);
    T_sum[rt]=T_sum[rt<<1]+T_sum[rt<<1|1];
}
 
int main()
{
    int n;
    scanf("%d",&n);
    for(int i=1;i<n;i++)
    {
        scanf("%d%d",&x,&y);
        f[x].push_back(y);
        f[y].push_back(x);
    }
    for(int i=1;i<=n;i++) scanf("%d",&val[i]);
    dfs1(1,0,1);
    dfs2(1,1);
    build(1,1,cnt);
    int z;char c[10];
    scanf("%d",&z);
    for(int i=1;i<=z;i++)
    {
        scanf("%s",c);
        if(c[0]=='C')
        {
            scanf("%d%d",&x,&y);
            query_change(1,1,cnt,id[x],y);
        }
        if(c[0]=='Q')
        {
            if(c[1]=='S')
            {
                scanf("%d%d",&x,&y);
                printf("%d\n",get_sum(x,y));
            }
            if(c[1]=='M')
            {
                scanf("%d%d",&x,&y);
                printf("%d\n",get_max(x,y));
            }
        }
    }
    return 0;
}