[洛谷P3833][SHOI2012]魔法树

题目大意：给一棵树，路径加，子树求和

题解：树剖

卡点：无

C++ Code：

#include <cstdio>
#include <iostream>
#define maxn 100010

int head[maxn], cnt;
struct Edge {
	int to, nxt;
} e[maxn << 1];
inline void add(int a, int b) {
	e[++cnt] = (Edge) {b, head[a]}; head[a] = cnt;
}

int n, m;

namespace SgT {
	long long V[maxn << 2], tg[maxn << 2];
	int L, R, num;

	inline void pushdown(int rt, int len) {
		long long &__tg = tg[rt];
		V[rt << 1] += __tg * (len + 1 >> 1);
		V[rt << 1 | 1] += __tg * (len >> 1);
		tg[rt << 1] += __tg;
		tg[rt << 1 | 1] += __tg;
		__tg = 0;
	}
	void __add(int rt, int l, int r) {
		if (L <= l && R >= r) {
			V[rt] += static_cast<long long> (r - l + 1) * num;
			tg[rt] += num;
			return ;
		}
		int mid = l + r >> 1;
		if (tg[rt]) pushdown(rt, r - l + 1);
		if (L <= mid) __add(rt << 1, l, mid);
		if (R > mid) __add(rt << 1 | 1, mid + 1, r);
		V[rt] = V[rt << 1] + V[rt << 1 | 1];
	}
	void add(int __L, int __R, int __num) {
		L = __L, R = __R, num = __num;
		__add(1, 1, n);
	}

	long long __ask(int rt, int l, int r) {
		if (L <= l && R >= r) return V[rt];
		int mid = l + r >> 1;
		long long ans = 0;
		if (tg[rt]) pushdown(rt, r - l + 1);
		if (L <= mid) ans = __ask(rt << 1, l, mid);
		if (R > mid) ans += __ask(rt << 1 | 1, mid + 1, r);
		return ans;
	}
	long long ask(int __L, int __R) {
		L = __L, R = __R;
		return __ask(1, 1, n);
	}
}
using SgT::add;
using SgT::ask;

int fa[maxn], dep[maxn], sz[maxn];
int dfn[maxn], idx, top[maxn], son[maxn];
void dfs1(int u) {
	sz[u] = 1;
	for (int i = head[u]; i; i = e[i].nxt) {
		int v = e[i].to;
		if (v != fa[u]) {
			fa[v] = u;
			dep[v] = dep[u] + 1;
			dfs1(v);
			sz[u] += sz[v];
			if (!son[u] || sz[v] > sz[son[u]]) son[u] = v;
		}
	}
}
void dfs2(int u) {
	dfn[u] = ++idx;
	int v = son[u];
	if (v) top[v] = top[u], dfs2(v);
	for (int i = head[u]; i; i = e[i].nxt) {
		v = e[i].to;
		if (v != fa[u] && v != son[u]) {
			top[v] = v;
			dfs2(v);
		}
	}
}

void modify(int x, int y, int z) {
	while (top[x] != top[y]) {
		if (dep[top[x]] < dep[top[y]]) std::swap(x, y);
		add(dfn[top[x]], dfn[x], z);
		x = fa[top[x]];
	}
	if (dep[x] > dep[y]) std::swap(x, y);
	add(dfn[x], dfn[y], z);
}
long long query(int x) {
	return ask(dfn[x], dfn[x] + sz[x] - 1);
}
int main() {
	std::ios::sync_with_stdio(false), std::cin.tie(0), std::cout.tie(0);
	std::cin >> n;
	for (int i = 1, a, b; i < n; i++) {
		std::cin >> a >> b; a++, b++;
		add(a, b);
		add(b, a);
	}
	dfs1(1);
	top[1] = 1;
	dfs2(1);
	std::cin >> m;
	while (m --> 0) {
		char op;
		int x, y, z;
		std::cin >> op >> x; x++;
		if (op == 'A') {
			std::cin >> y >> z; y++;
			modify(x, y, z);
		} else std::cout << query(x) << '\n';
	}
	return 0;
}