BZOJ 1036 [ZJOI2008]树的统计Count (树链剖分

题目链接：http://www.lydsy.com/JudgeOnline/problem.php?id=1036

树链剖分模版题，打的时候注意点就行。做这题的时候，真的傻了，单词拼错检查了一个多小时...

代码如下：

//树链剖分 点权修改 修改单节点
#include <iostream>
#include <cstring>
#include <algorithm>
#include <cstdio>
using namespace std;
const int MAXN = 3e4 + 10;
struct data {
    int to , next;
}edge[MAXN << 1];
int head[MAXN] , cnt , tot;
int top[MAXN] , par[MAXN] , son[MAXN] , size[MAXN] , dep[MAXN];
int id[MAXN] , fid[MAXN]; //id[i]表示i对应在线段树上的位置 fid[i]表示线段树位置是i的叶子 对应的节点 
int a[MAXN];

void init() {
    tot = cnt = 0;
    memset(head , -1 , sizeof(head));
}

inline void add(int u , int v) {
    edge[tot].next = head[u];
    edge[tot].to = v;
    head[u] = tot++;
}

void dfs1(int u , int p , int d) {
    dep[u] = d , size[u] = 1 , son[u] = u , par[u] = p;
    for(int i = head[u] ; ~i ; i = edge[i].next) {
        int v = edge[i].to;
        if(v == p)
            continue;
        dfs1(v , u , d + 1);
        if(size[v] >= size[son[u]] || son[u] == u)
            son[u] = v;
        size[u] += size[v];
    }
}

void dfs2(int u , int p , int t) {
    top[u] = t , id[u] = ++cnt;
    fid[cnt] = u;
    if(son[u] != u)
        dfs2(son[u] , u , t);
    for(int i = head[u] ; ~i ; i = edge[i].next) {
        int v = edge[i].to;
        if(v == p || v == son[u])
            continue;
        dfs2(v , u , v);
    }
}

struct segtree {
    int l , r;
    int sum , Max;
}T[MAXN << 2];

void build(int p , int l , int r) {
    int mid = (l + r) >> 1;
    T[p].l = l , T[p].r = r;
    if(l == r) {
        T[p].Max = T[p].sum = a[fid[l]]; //
        return ;
    }
    build(p << 1 , l , mid);
    build((p << 1)|1 , mid + 1 , r);
    T[p].sum = T[p << 1].sum + T[(p << 1)|1].sum;
    T[p].Max = max(T[p << 1].Max , T[(p << 1)|1].Max);
}

void updata(int p , int pos , int num) {
    int mid = (T[p].l + T[p].r) >> 1;
    if(T[p].l == T[p].r && T[p].l == pos) {
        T[p].sum = T[p].Max = num;
        return ;
    }
    if(pos <= mid) {
        updata(p << 1 , pos , num);
    }
    else {
        updata((p << 1)|1 , pos , num);
    }
    T[p].sum = T[p << 1].sum + T[(p << 1)|1].sum;
    T[p].Max = max(T[p << 1].Max , T[(p << 1)|1].Max);
}

int query_sum(int p , int l , int r) {
    int mid = (T[p].l + T[p].r) >> 1;
    if(T[p].l == l && T[p].r == r) {
        return T[p].sum;
    }
    if(r <= mid) {
        return query_sum(p << 1 , l , r);
    }
    else if(l > mid) {
        return query_sum((p << 1)|1 , l , r);
    }
    else {
        return query_sum(p << 1 , l , mid) + query_sum((p << 1)|1 , mid + 1 , r);
    }
}

int query_max(int p , int l , int r) {
    int mid = (T[p].l + T[p].r) >> 1;
    if(T[p].l == l && T[p].r == r) {
        return T[p].Max;
    }
    if(r <= mid) {
        return query_max(p << 1 , l , r);
    }
    else if(l > mid) {
        return query_max((p << 1)|1 , l , r);
    }
    else {
        return max(query_max(p << 1 , l , mid) , query_max((p << 1)|1 , mid + 1 , r));
    }
}

int find_max(int u , int v) {
    int fu = top[u] , fv = top[v];
    int Max = -1000000000;    
    while(fu != fv) {
        if(dep[fu] >= dep[fv]) {
            Max = max(Max , query_max(1 , id[fu] , id[u]));
            u = par[fu];
            fu = top[u];
        }
        else {
            Max = max(Max , query_max(1 , id[fv] , id[v]));
            v = par[fv];
            fv = top[v];
        }
    }
    if(dep[u] >= dep[v]) {
        return max(Max , query_max(1 , id[v] , id[u]));
    }
    else {
        return max(Max , query_max(1 , id[u] , id[v]));
    }
}

int find_sum(int u , int v) {
    int fu = top[u] , fv = top[v];
    int sum = 0;
    while(fu != fv) {
        if(dep[fu] > dep[fv]) {
            sum += query_sum(1 , id[fu] , id[u]);
            u = par[fu];
            fu = top[u];
        }
        else {
            sum += query_sum(1 , id[fv] , id[v]);
            v = par[fv];
            fv = top[v];
        }
    }
    if(dep[u] >= dep[v]) {
        return (sum + query_sum(1 , id[v] , id[u]));
    }
    else {
        return (sum + query_sum(1 , id[u] , id[v]));
    }
}

int main()
{
    int n , u , v;
    while(~scanf("%d" , &n)) {
        init();
        for(int i = 1 ; i < n ; ++i) {
            scanf("%d %d" , &u , &v);
            add(u , v);
            add(v , u);
        }
        for(int i = 1 ; i <= n ; ++i) {
            scanf("%d" , a + i);
        }
        cnt = 0;
        dfs1(1 , 1 , 0);
        dfs2(1 , 1 , 1);
        build(1 , 1 , cnt);
        int m;
        char q[10];
        scanf("%d" , &m);
        while(m--) {
            scanf("%s%d%d" , q , &u , &v);
            if(q[0] == 'C') {
                updata(1 , id[u] , v);
            }
            else if(strcmp(q ,"QMAX") == 0) {
                printf("%d
" , find_max(u , v));
            }
            else {
                printf("%d
", find_sum(u , v));
            }
        }
    }
    return 0;
}