P2590 [ZJOI2008]树的统计

久违的树剖~

#include <vector>
#include <cstdio>
#include <cstring>
#include <cassert>
#include <iostream>
#include <algorithm>
using namespace std;
const int MAXN = 3e4 + 10;
inline int read(){
	char ch = getchar(); int x = 0; bool flag = false;
	while(!isdigit(ch)) flag |= (ch == '-'), ch = getchar();
	while(isdigit(ch)) x = x * 10 + ch - '0', ch = getchar();
	return flag ? -x : x;
}

int N, val[MAXN];
vector<int> g[MAXN];

int fa[MAXN], dep[MAXN], siz[MAXN], son[MAXN];
int dfs1(int u, int f, int depth){
	dep[u] = depth, fa[u] = f, siz[u] = 1;

	int tmp = -1;
	for(int i = 0; i < (int) g[u].size(); i++){
		int &v = g[u][i];
		if(v == f) continue;

		siz[u] += dfs1(v, u, depth + 1);
		if(tmp == -1 || siz[v] > siz[tmp]) tmp = v;
	}
	son[u] = tmp; return siz[u];
}

int top[MAXN], idx[MAXN], reidx[MAXN];
void dfs2(int u, int t){
	static int cntnode = 0;
	idx[u] = ++cntnode, top[u] = t, reidx[cntnode] = u;

	if(son[u] == -1) return;

	dfs2(son[u], t);
	for(int i = 0; i < (int) g[u].size(); i++){
		int &v = g[u][i];
		if(v == fa[u] || v == son[u]) continue;
		dfs2(v, v);
	}
}

namespace stree
{
	#define mid ((l + r) >> 1)
	#define ls (o << 1)
	#define rs ((o << 1) | 1)

	struct Node
	{
		int sum, val;
	}node[MAXN << 2];

	inline void pushup(int o){
		node[o].sum = node[ls].sum + node[rs].sum,
		node[o].val = max(node[ls].val, node[rs].val);
	}
                         
	void build(int o, int l, int r){
		if(l == r) return node[o].val = node[o].sum = val[reidx[l]], void();
		build(ls, l, mid), build(rs, mid + 1, r);
		return pushup(o);
	}

	void modify(int o, int l, int r, int p, int v){
		if(l == r) return node[o].val = node[o].sum = v, void();
		if(p <= mid) modify(ls, l, mid, p, v);
		else modify(rs, mid + 1, r, p, v);
		return pushup(o);
	}

	int query(int o, int l, int r, int a, int b, bool type) { //true -> max, false -> sum
		if(l > b || r < a) return type ? -(1 << 30) : 0;
		if(a <= l && r <= b) return type ? node[o].val : node[o].sum;
		if(type) return max(query(ls, l, mid, a, b, true), query(rs, mid + 1, r, a, b, true));
		else return query(ls, l, mid, a, b, false) + query(rs, mid + 1, r, a, b, false);
	}
}

int main(){
	// freopen("p2590.in", "r", stdin);
	// freopen("p2590.out", "w", stdout); 
	cin>>N;
	for(int i = 1; i < N; i++){
		int u = read(), v = read();
		g[u].push_back(v), g[v].push_back(u);
	}
	for(int i = 1; i <= N; i++) val[i] = read();
	dfs1(1, 0, 1), dfs2(1, 1);
	memset(stree::node, -0x3f, sizeof(stree::node));
	stree::build(1, 1, N);
	int Q; cin>>Q; char ch[10];
	while(Q--){
		using namespace stree;
		scanf(" %[A-Z]", ch); int u = read(), v = read();
		
		if(ch[0] == 'C')
			modify(1, 1, N, idx[u], v);
		else {
			if(ch[1] == 'M'){
				int ans = -(1 << 30);
				while(top[u] != top[v]) {
					if(dep[top[u]] < dep[top[v]]) swap(u, v);
					ans = max(ans, query(1, 1, N, idx[top[u]], idx[u], true));
					u = fa[top[u]];
				}
				if(dep[u] < dep[v]) swap(u, v);
				ans = max(ans, query(1, 1, N, idx[v], idx[u], true));
				printf("%d
", ans);
			}
			else {
				int ans = 0;
				while(top[u] != top[v]) {
					if(dep[top[u]] < dep[top[v]]) swap(u, v);
					ans += query(1, 1, N, idx[top[u]], idx[u], false);
					u = fa[top[u]];
				}
				if(dep[u] < dep[v]) swap(u, v);
				ans += query(1, 1, N, idx[v], idx[u], false);
				printf("%d
", ans);
			}
		}
	}
	return 0;
}