bzoj 1036 树的统计Count

题意：...

解法：树链剖分，对点进行重编号，这样的话线段树中点的信息就是树中点的信息。。。别的很常规。。。

#include<cstdio>
#include<cstring>
#include<algorithm>
#define N 30010
#define lson l,m,n<<1
#define rson m+1,r,n<<1|1
using namespace std;
const int inf=1<<30;
struct Edge{
    int u,v,next;
    Edge(){}
    Edge(int _u,int _v,int _next){
        u=_u;v=_v;next=_next;
    }
}edge[N<<1];
int head[N],cnt;
int sz[N],top[N],fa[N],dep[N],hash[N],w[N],son[N],num;
void init(){
    memset(head,-1,sizeof(head));
    cnt=num=0;
}
void add(int u,int v){
    edge[cnt]=Edge(u,v,head[u]);head[u]=cnt++;
    edge[cnt]=Edge(v,u,head[v]);head[v]=cnt++;
}
void dfs(int u,int d){
    sz[u]=1;son[u]=0;dep[u]=d;
    for(int k=head[u];k!=-1;k=edge[k].next){
        int v=edge[k].v;
        if(v==fa[u])continue;
        fa[v]=u;
        dfs(v,d+1);
        sz[u]+=sz[v];
        if(sz[v]>sz[son[u]])son[u]=v;
    }
}
void build_tree(int u,int pre){
    hash[u]=++num;top[u]=pre;
    if(son[u])build_tree(son[u],pre);
    for(int k=head[u];k!=-1;k=edge[k].next){
        int v=edge[k].v;
        if(v!=fa[u]&&v!=son[u])build_tree(v,v);
    }
}
struct segtree{
    int maxn[N<<2],sum[N<<2];
    void pushup(int n){
        sum[n]=sum[n<<1]+sum[n<<1|1];
        maxn[n]=max(maxn[n<<1],maxn[n<<1|1]);
    }
    void update(int nn,int x,int l,int r,int n){
        if(l==r){
            maxn[n]=sum[n]=x;
            return;
        }
        int m=(l+r)>>1;
        if(nn<=m)update(nn,x,lson);
        else update(nn,x,rson);
        pushup(n);
    }
    int query_max(int ll,int rr,int l,int r,int n){
        if(ll==l&&rr==r)return maxn[n];
        int m=(l+r)>>1;
        if(rr<=m)return query_max(ll,rr,lson);
        else if(ll>m)return query_max(ll,rr,rson);
        else return max(query_max(ll,m,lson),query_max(m+1,rr,rson));
    }
    int query_sum(int ll,int rr,int l,int r,int n){
        if(ll==l&&rr==r)return sum[n];
        int m=(l+r)>>1;
        if(rr<=m)return query_sum(ll,rr,lson);
        else if(ll>m)return query_sum(ll,rr,rson);
        else return query_sum(ll,m,lson)+query_sum(m+1,rr,rson);
    }
}seg;
int Query_max(int a,int b,int n){
    int ta=top[a],tb=top[b],ans=-inf;
    while(ta!=tb){
        if(dep[ta]<dep[tb]){
            swap(ta,tb);swap(a,b);
        }
        ans=max(ans,seg.query_max(hash[ta],hash[a],1,n,1));
        a=fa[ta];ta=top[a];
    }
    if(dep[a]>dep[b])swap(a,b);
    return max(ans,seg.query_max(hash[a],hash[b],1,n,1));
}
int Query_sum(int a,int b,int n){
    int ta=top[a],tb=top[b],ans=0;
    while(ta!=tb){
        if(dep[ta]<dep[tb]){
            swap(ta,tb);swap(a,b);
        }
        ans+=seg.query_sum(hash[ta],hash[a],1,n,1);
        a=fa[ta];ta=top[a];
    }
    if(dep[a]>dep[b])swap(a,b);
    return ans+seg.query_sum(hash[a],hash[b],1,n,1);
}
int main(){
    int n,a,b,q;
    char op[10];
    while(~scanf("%d",&n)){
        init();
        for(int i=1;i<n;i++){
            scanf("%d%d",&a,&b);
            add(a,b);
        }
        for(int i=1;i<=n;i++)scanf("%d",&w[i]);
        dfs(1,1);
        build_tree(1,1);
        for(int i=1;i<=n;i++)seg.update(hash[i],w[i],1,n,1);
        scanf("%d",&q);
        while(q--){
            scanf("%s%d%d",op,&a,&b);
            if(strcmp(op,"QMAX")==0){
                int ans=Query_max(a,b,n);
                printf("%d\n",ans);
            }else if(strcmp(op,"QSUM")==0){
                int ans=Query_sum(a,b,n);
                printf("%d\n",ans);
            }else {
                seg.update(hash[a],b,1,n,1);
            }
        }
    }
    return 0;
}