bzoj1036点权模板题

/*
HYSBZ1036
树上有1-n个结点，每个节点都有一个权值w
操作 CHANGE u t:把结点u的权值改为t
     QMAX u v:询问从点u到v的路径上的节点的最大权值
     QSUM u v:询问从点u到v的路径上的结点的权值和
从点u到点v路径上的结点包括u，v本身

*/
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#define MAXN 30010
using namespace std;
struct Edge{
    int to, next;
}edge[MAXN*];
int head[MAXN], tot;
int top[MAXN];//重链顶端
int fa[MAXN];//父亲
int deep[MAXN];//深度，root=1
int num[MAXN];//子节点数
int p[MAXN];//v在线段树中的位置
int fp[MAXN];
int son[MAXN];//重儿子
int pos;
void init(){
    tot = ;
    memset(head, -, sizeof(head));
    pos = ;
    memset(son, -, sizeof(son));
}
void addedge(int u, int v){
    edge[tot].to = v;
    edge[tot].next = head[u];
    head[u] = tot++;
}
//第一次dfs求fa,deep,son,num
void dfs1(int u, int pre, int d){
    deep[u] = d;
    fa[u] = pre;
    num[u] = ;
    for(int i = head[u]; i != -; i = edge[i].next){
        int v = edge[i].to;
        if (v != pre){
            dfs1(v, u, d+);
            num[u]+=num[v];
            if (son[u]==-||num[v]>num[son[u]])
                son[u] = v;
        }
    }
}
//第二次dfs求top，p,用pos记数
void getpos(int u, int sp){//sp表示重链顶端
    top[u] = sp;
    p[u] = pos++;
    fp[p[u]] = u;
    if (son[u]==-)
        return;
    getpos(son[u], sp);//先把重儿子查到底
    for(int i = head[u]; i != -; i = edge[i].next){
        int v = edge[i].to;//轻儿子
        if (v != son[u] && v != fa[u])
            getpos(v, v);
    }
}

//线段树部分
struct Node{
    int l, r;
    int sum;
    int Max;
}segTree[MAXN*];
inline void push_up(int i){
    segTree[i].sum = segTree[i<<].sum + segTree[i<<|].sum;
    segTree[i].Max = max(segTree[i<<].Max, segTree[i<<|].Max);
}
int s[MAXN];
void build(int i, int l, int r){
    segTree[i].l = l;
    segTree[i].r = r;

    if (l==r){
        segTree[i].sum = segTree[i].Max = s[fp[l]];
        return;
    }

    int mid = l+r >> ;
    build(i<<, l, mid);
    build(i<<|, mid+, r);
    push_up(i);
}
//更新线段树的第k个值为val
void update(int i, int k, int val){
    if(segTree[i].l == k && segTree[i].r == k){
        segTree[i].Max = segTree[i].sum = val;
        return;
    }
    int mid = segTree[i].l + segTree[i].r >> ;
    if (k <= mid)
        update(i<<, k, val);
    else
        update(i<<|, k, val);
    push_up(i);//单点更新后要重新计算Max和Sum
}
//查询[l,r]区间的最大值
int queryMax(int i, int l, int r){
    if(segTree[i].l == l && segTree[i].r == r)
        return segTree[i].Max;
    int mid = segTree[i].l+segTree[i].r >> ;
    if (r <= mid)
        return queryMax(i<<, l, r);
    else if (l > mid)
        return queryMax(i<<|, l, r);
    else
        return max(queryMax(i<<, l, mid), queryMax(i<<|, mid+, r));
}
//查询[l,r]区间的和
int querySum(int i, int l, int r){
    if(segTree[i].l==l && segTree[i].r == r)
        return segTree[i].sum;
    int mid = segTree[i].l+segTree[i].r>>;
    if(r <= mid)
        return querySum(i<<,l,r);
    else if(l > mid)
        return querySum((i<<)|,l,r);
    else
        return querySum(i<<, l, mid)+querySum(i<<|, mid+, r);
}
//查询u->v路径上结点的最大权值
int findMax(int u, int v){
    int f1 = top[u], f2 = top[v];
    int tmp = -;
    while(f1!=f2){//不在同一条重链上时
        if(deep[f1]<deep[f2]){
            swap(u, v);
            swap(f1, f2);
        }
        tmp = max(tmp, queryMax(, p[f1], p[u]));//把这一条链上的求出来
        u = fa[f1];
        f1 = top[u];
    }
    if (deep[u]>deep[v])
        swap(u,v);
    return
        max(tmp, queryMax(, p[u], p[v]));

}
//查询u->v路径上结点的权值
int findSum(int u, int v){
    int f1 = top[u];
    int f2 = top[v];
    int tmp = ;
    while(f1 != f2){
        if (deep[f1] < deep[f2]){
            swap(f1, f2);
            swap(u, v);
        }
        tmp += querySum(, p[f1], p[u]);
        u = fa[f1];
        f1 = top[u];
    }
    if(deep[u]>deep[v])
        swap(u, v);
    return tmp + querySum(, p[u], p[v]);
}

int main(){
    int n;
    int q;
    char op[];
    int u, v;
    while(scanf("%d", &n)==){
        init();
        for(int i = ; i < n; i++){
            scanf("%d%d", &u, &v);
            addedge(u, v);
            addedge(v, u);
        }
        for(int i = ; i <= n; i++)
            scanf("%d", &s[i]);

        dfs1(,,);
        getpos(,);
        build(, , pos-);

        scanf("%d", &q);
        while(q--){
            scanf("%s%d%d", op, &u, &v);
            if (op[]=='C')
                update(, p[u], v);//单点修改
            else if (strcmp(op, "QMAX")==)
                printf("%d\n", findMax(u, v));//查询u->v路径上点权的最大值
            else
                printf("%d\n", findSum(u, v));//查询路径上点权的和
        }
    }
    return ;
}