[HEOI2016/TJOI2016]树

Description

[HEOI2016/TJOI2016]树

Solution

树剖裸题，以为会爆栈（然而却是爆栈了，但是不知道怎么改）
剖成链之后，每段链的线段树维护区间最大值（因为DFS序大的肯定离点近）

Code

#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize("Ofast")
#pragma GCC optimize("inline")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-fipa-sra")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fdevirtualize")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-fwhole-program")
#pragma GCC optimize("-freorder-blocks")
#pragma GCC optimize("-fschedule-insns")
#pragma GCC optimize("inline-functions")
#pragma GCC optimize("-ftree-tail-merge")
#pragma GCC optimize("-fschedule-insns2")
#pragma GCC optimize("-fstrict-aliasing")
#pragma GCC optimize("-fstrict-overflow")
#pragma GCC optimize("-falign-functions")
#pragma GCC optimize("-fcse-skip-blocks")
#pragma GCC optimize("-fcse-follow-jumps")
#pragma GCC optimize("-fsched-interblock")
#pragma GCC optimize("-fpartial-inlining")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-fhoist-adjacent-loads")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("inline-small-functions")
#pragma GCC optimize("-finline-small-functions")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("-funsafe-loop-optimizations")
#pragma GCC optimize("inline-functions-called-once")
#pragma GCC optimize("-fdelete-null-pointer-checks")
#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
#define MAXN 800010
struct rec {
	int nxt, ver;
} t[MAXN];
struct Rec {
	int val;
} tree[MAXN];
int n, q, cnt, u, v, x, s;
int head[MAXN], Top[MAXN], Fa[MAXN], h[MAXN], H[MAXN];
char ch;
bool vis[MAXN];
inline int read() {
	int s = 0, w = 1;
	char c = getchar();
	for (; !isdigit(c); c = getchar()) if (c == '-') w = -1;
	for (; isdigit(c); c = getchar()) s = (s << 1) + (s << 3) + (c ^ 48);
	return s * w;
}
inline void add(int u, int v) {
	t[++cnt].nxt = head[u], t[cnt].ver = v, head[u] = cnt;
}
void DFS(int u, int fa) {
	vis[u] = true, Top[u] = fa, h[u] = ++s, H[s] = u;
	for (register int i = head[u]; i; i = t[i].nxt) {
		int v = t[i].ver;
		if (!vis[v])
			Fa[v] = u, DFS(v, fa);
		break;
	}
	for (register int i = head[u]; i; i = t[i].nxt) {
		int v = t[i].ver;
		if (!vis[v])
			Fa[v] = u, DFS(v, v);
	}
}
inline void update(int now) {
	tree[now].val = max(tree[now << 1].val, tree[now << 1 | 1].val);
}
void Modify(int now, int l, int r, int k) {
	#define mid ((l + r) >> 1)
	if (l == r) {
		tree[now].val = max(tree[now].val, k);
		return;
	}
	if (k <= mid) Modify(now << 1, l, mid, k);
	else Modify(now << 1 | 1, mid + 1, r, k);
	update(now);
	#undef mid
}
int Query(int now, int l, int r, int x, int y) {
	int ans = 0;
	#define mid ((l + r) >> 1)
	if (x <= l && r <= y)
		return max(ans, tree[now].val);
	if (x <= mid) ans = max(ans, Query(now << 1, l, mid, x, y));
	if (mid < y) ans = max(ans, Query(now << 1 | 1, mid + 1, r, x, y));
	return ans;
	#undef mid
}
int fuck(int now) {
	while (now) {
		s = Query(1, 1, n, h[Top[now]], h[now]);
		if (s) return H[s];
		now = Fa[Top[now]];
	}
}
int main() {
	freopen("pa.in", "r", stdin);
	freopen("pa.out", "w", stdout);
	n = read(), q = read();
	for (register int i = 1; i <= n - 1; i++)
		u = read(), v = read(), add(u, v), add(v, u);
	DFS(1, 1);
	Modify(1, 1, n, 1);
	while (q--) {
		ch = getchar();
		if (ch == 'Q') {
			x = read();
			printf("%d\n", fuck(x));
		}
		if (ch == 'C') {
			x = read();
			Modify(1, 1, n, h[x]);
		}
	}
	return 0;
}