BZOJ 1036 树的统计（树链剖分）

点权树链剖分模板题。

# include <cstdio>
# include <cstring>
# include <cstdlib>
# include <iostream>
# include <vector>
# include <queue>
# include <stack>
# include <map>
# include <set>
# include <cmath>
# include <algorithm>
using namespace std;
# define lowbit(x) ((x)&(-x))
# define pi acos(-1.0)
# define eps 1e-9
# define MOD 1000000007
# define INF 1000000000
# define mem(a,b) memset(a,b,sizeof(a))
# define FOR(i,a,n) for(int i=a; i<=n; ++i)
# define FO(i,a,n) for(int i=a; i<n; ++i)
# define bug puts("H");
# define lch p<<1,l,mid
# define rch p<<1|1,mid+1,r
# define mp make_pair
# define pb push_back
typedef pair<int,int> PII;
typedef vector<int> VI;
# pragma comment(linker, "/STACK:1024000000,1024000000")
typedef long long LL;
int Scan() {
    int res=0, flag=0;
    char ch;
    if((ch=getchar())=='-') flag=1;
    else if(ch>='0'&&ch<='9') res=ch-'0';
    while((ch=getchar())>='0'&&ch<='9')  res=res*10+(ch-'0');
    return flag?-res:res;
}
void Out(int a) {
    if(a<0) {putchar('-'); a=-a;}
    if(a>=10) Out(a/10);
    putchar(a%10+'0');
}
const int N=30005;
//Code begin...

struct Edge{int p, next;}edge[N<<1];
int head[N], cnt, node[N], n;
int seg[N<<2][2], fa[N], size[N], dep[N], p[N], top[N], son[N], pos;

void add_edge(int u, int v){edge[cnt].p=v; edge[cnt].next=head[u]; head[u]=cnt++;}
void init(){cnt=1; mem(son,-1); pos=1;}
void dfs(int x, int pre, int d)
{
    fa[x]=pre; dep[x]=d; size[x]=1;
    for (int i=head[x]; i; i=edge[i].next) {
        int v=edge[i].p;
        if (v==pre) continue;
        dfs(v,x,d+1);
        size[x]+=size[v];
        if (son[x]==-1||size[v]>size[son[x]]) son[x]=v;
    }
}
void get_pos(int x, int sp)
{
    top[x]=sp; p[x]=pos++;
    if (son[x]==-1) return ;
    get_pos(son[x],sp);
    for (int i=head[x]; i; i=edge[i].next) {
        int v=edge[i].p;
        if (v!=son[x]&&v!=fa[x]) get_pos(v,v);
    }
}
void push_up(int p)
{
    seg[p][0]=max(seg[p<<1][0], seg[p<<1|1][0]);
    seg[p][1]=seg[p<<1][1]+seg[p<<1|1][1];
}
void update(int p, int l, int r, int L, int val)
{
    if (L>r||L<l) return ;
    if (L==l&&L==r) seg[p][0]=seg[p][1]=val;
    else {
        int mid=(l+r)>>1;
        update(lch,L,val); update(rch,L,val);
        push_up(p);
    }
}
int query(int p, int l, int r, int L, int R, int flag)
{
    if (L>r||R<l) {
        if (flag) return 0;
        else return -INF;
    }
    if (L<=l&&R>=r) return seg[p][flag];
    int mid=(l+r)>>1;
    if (flag) return query(lch,L,R,flag)+query(rch,L,R,flag);
    else return max(query(lch,L,R,flag),query(rch,L,R,flag));
}
int Qtree(int l, int r, int flag)
{
    int f1=top[l], f2=top[r], ans;
    if (flag) ans=0;
    else ans=-INF;
    bool mark=false;
    while (f1!=f2) {
        mark=true;
        if (dep[f1]<dep[f2]) swap(f1,f2), swap(l,r);
        if (flag==0) ans=max(ans,query(1,1,n,p[f1],p[l],flag));
        else ans+=query(1,1,n,p[f1],p[l],flag);
        l=fa[f1]; f1=top[l];
    }
    if (dep[l]>dep[r]) swap(l,r);
    if (flag==0) ans=max(ans,query(1,1,n,p[l],p[r],flag));
    else ans+=query(1,1,n,p[l],p[r],flag);
    return ans;
}
int main ()
{
    int u, v, q, l, r;
    char flag[10];
    init();
    scanf("%d",&n);
    FO(i,1,n) scanf("%d%d",&u,&v), add_edge(u,v), add_edge(v,u);
    dfs(1,0,0);
    get_pos(1,1);
    FOR(i,1,n) scanf("%d",node+i), update(1,1,n,p[i],node[i]);
    scanf("%d",&q);
    while (q--) {
        scanf("%s%d%d",flag,&l,&r);
        if (flag[0]=='C') update(1,1,n,p[l],r);
        else printf("%d\n",Qtree(l,r,flag[1]=='S'));
    }
    return 0;
}