luoguP3071 [USACO13JAN]座位Seating

https://www.luogu.org/problem/P3071

AC代码：

https://www.luogu.org/blog/user33426/solution-p3071

莫名其妙RE：

#include<cstdio>
#include<iostream>

using namespace std;
#define MAX 500005
#define lson o<<1
#define rson o<<1|1

int n,m,ans,cnt;
int addv[MAX];
struct node{
	int lm, rm, xm;
	//从左到右的最大空位置的数
	//从右到左的
	//整个的
}tr[MAX<<2];

inline int max(int x,int y) {
	return x>y?x:y;
}

void push_up(int o, int l, int r) {
	tr[o].xm = max(max(tr[lson].xm , tr[rson].xm ), tr[lson].rm + tr[rson].lm );
	int mid = (l+r)>>1;
	if(tr[lson].xm == mid-l+1) tr[o].lm = tr[lson].xm + tr[rson].lm ;
	else tr[o].lm = tr[lson].lm ;
	if(tr[rson].xm == r-mid) tr[o].rm = tr[rson].xm + tr[lson].rm ;
	else tr[o].rm = tr[rson].rm ;
}
void build(int o, int l, int r) {
	if(l == r) {
		tr[o].lm = tr[o].rm = tr[o].xm = 1;
		return ;
	}
	int mid = (l+r)>>1;
	build(lson, l, mid);
	build(rson, mid+1, r);
	push_up(o, l, r);
}

void pushtag(int o) {
	tr[o].lm = tr[o].rm = tr[o].xm = 0;
	addv[o] = 1;
}
void push_down(int o, int l, int r) {
	if(addv[o] == 0) return ;
	int mid = (l+r)>>1;
	tr[lson].lm = tr[lson].rm = tr[lson].xm = addv[o]>0 ? 0 : (mid-l+1);  //-1为离开
	tr[rson].lm = tr[rson].rm = tr[rson].xm = addv[o]>0 ? 0 : (r-mid); //1为坐下
	addv[lson] = addv[rson] = addv[o];
	addv[o] = 0;
	return ;
} 

void insert(int o, int l, int r, int a, int op) {//op=1表示前a个改为1，即前a个坐下， op=2表示后a个改为1
//	printf("%d %d %d %d %d", o, l, r, a, op);
//	printf("\n");
	if(a == 0) return ;
	if(r-l+1 == a) {pushtag(o); return ;}
	int mid = (l+r)>>1;
	push_down(o, l, r);
	if(op == 1) {
		if(tr[lson].xm >= a) insert(lson, l, mid, a, 1);
		else if(tr[lson].rm + tr[rson].lm >= a) {
			insert(rson, mid+1, r, a-tr[lson].rm , 1); //这个顺序太莫名其妙了....
			insert(lson, l, mid+1, tr[lson].rm , 2);//因为是从前往后，所以lson肯定是坐下tr[lson].r个
			}
		else insert(rson, mid+1, r, a, 1);//
	} else {
		if(tr[rson].xm >= a) insert(rson, mid+1, r, a, 2);
		else if(tr[lson].rm + tr[rson].lm >= a){
			insert(lson, l, mid, a-tr[rson].lm , 2);
			insert(rson, mid+1, r, tr[rson].lm , 1);
		}
		else insert(lson, l, mid, a, 2);
	}
	push_up(o, l, r);
}

void del(int o, int l, int r, int ql, int qr) {
	if(qr<l||r<ql) return;
	if(ql <= l && r <= qr) {
		tr[o].lm = tr[o].rm = tr[o].xm = (r-l+1);
		addv[o] = -1;
		return ;
	}
	int mid = (l+r)>>1;
	push_down(o, l, r);
	del(lson, l, mid, ql, qr);
	del(rson, mid+1, r, ql, qr);
	push_up(o,l,r);
}

int main() {
	scanf("%d%d",&n,&m);
	build(1, 1, n);
//	int tmp;
//	scanf("%d",&tmp);
//	printf("o : %d, %d", tmp, tr[tmp].lm);
	char cmd;
	while(m--) {
		cin>>cmd;
		if(cmd == 'A') {
			int a;
			scanf("%d",&a);
			if(tr[1].xm < a) ans++;
			else insert(1, 1, n, a, 1);
		} else {
			int x, y;
			scanf("%d%d",&x, &y);
			del(1, 1, n, x, y);
		}
	}
	printf("%d",ans);
}