[BZOJ1861][Zjoi2006]Book 书架

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <algorithm>
using namespace std;

int read() {
	int x = 0, f = 1; char c = getchar();
	while(!isdigit(c)){ if(c == ‘-‘) f = -1; c = getchar(); }
	while(isdigit(c)){ x = x * 10 + c - ‘0‘; c = getchar(); }
	return x * f;
}

#define maxn 80010
struct Node {
	int siz;
	Node() {}
} ns[maxn];
int ToT, fa[maxn], ch[2][maxn], id[maxn];
void maintain(int o) {
	ns[o].siz = 1;
	for(int i = 0; i < 2; i++) if(ch[i][o])
		ns[o].siz += ns[ch[i][o]].siz;
	return ;
}
void build(int& o, int l, int r) {
	if(l > r) return ;
	int mid = l + r >> 1; o = id[mid];
	build(ch[0][o], l, mid - 1); build(ch[1][o], mid + 1, r);
	if(ch[0][o]) fa[ch[0][o]] = o;
	if(ch[1][o]) fa[ch[1][o]] = o;
	return maintain(o);
}
void rotate(int u) {
	int y = fa[u], z = fa[y], l = 0, r = 1;
	if(z) ch[ch[1][z]==y][z] = u;
	if(ch[1][y] == u) swap(l, r);
	fa[u] = z; fa[y] = u; fa[ch[r][u]] = y;
	ch[l][y] = ch[r][u]; ch[r][u] = y;
	maintain(y); maintain(u);
	return ;
}
void splay(int u) {
	while(fa[u]) {
		int y = fa[u], z = fa[y];
		if(z) {
			if(ch[0][y] == u ^ ch[0][z] == y) rotate(u);
			else rotate(y);
		}
		rotate(u);
	}
	return ;
}
int splitl(int u) {
	splay(u);
	int tmp = ch[0][u];
	fa[tmp] = ch[0][u] = 0;
	maintain(u);
	return tmp;
}
int splitr(int u) {
	splay(u);
	int tmp = ch[1][u];
	fa[tmp] = ch[1][u] = 0;
	maintain(u);
	return tmp;
}
int merge(int a, int b) {
	if(!a) return maintain(b), b;
	if(!b) return maintain(a), a;
	while(ch[1][a]) a = ch[1][a];
	splay(a);
	ch[1][a] = b; fa[b] = a;
	return maintain(a), a;
}
int getrt() {
	int u = 1; while(fa[u]) u = fa[u];
	return u;
}
int Find(int o, int k) {
	if(!o) return 0;
	int ls = ch[0][o] ? ns[ch[0][o]].siz : 0;
	if(k == ls + 1) return o;
	if(k > ls + 1) return Find(ch[1][o], k - ls - 1);
	return Find(ch[0][o], k);
}

int main() {
	int n = read(), q = read();
	for(int i = 1; i <= n; i++) id[i] = read();
	int tmp = 0; build(tmp, 1, n);
	
	int tq = q;
	while(q--) {
		char cmd[10]; scanf("%s", cmd);
		if(cmd[0] == ‘T‘) {
			int mrt = read(), lrt = splitl(mrt), rrt = splitr(mrt);
			lrt = merge(lrt, rrt); merge(mrt, lrt);
		}
		if(cmd[0] == ‘B‘) {
			int mrt = read(), lrt = splitl(mrt), rrt = splitr(mrt);
			lrt = merge(lrt, rrt); merge(lrt, mrt);
		}
		if(cmd[0] == ‘I‘) {
			int mrt = read(), t = read(), rk, lrt, rrt;
			if(!t) continue;
			splay(mrt); rk = (ch[0][mrt] ? ns[ch[0][mrt]].siz : 0) + 1 + t;
			if(rk < 1 || rk > n) continue; rk = Find(getrt(), rk);
			if(t < 0) {
				lrt = splitl(rk); splitl(mrt); rrt = splitr(mrt);
				lrt = merge(lrt, mrt); lrt = merge(lrt, rk); merge(lrt, rrt);
			}
			else {
				lrt = splitl(mrt); splitl(rk); rrt = splitr(rk);
				lrt = merge(lrt, rk); lrt = merge(lrt, mrt); merge(lrt, rrt);
			}
		}
		if(cmd[0] == ‘A‘) {
			int u = read();
			splay(u);
			printf("%d\n", ch[0][u] ? ns[ch[0][u]].siz : 0);
		}
		if(cmd[0] == ‘Q‘) printf("%d\n", Find(getrt(), read()));
	}
	
	return 0;
}