P3391 【模板】文艺平衡树

题目链接

感觉比普通平衡树易懂

代码：

#include<bits/stdc++.h>
using namespace std;

const int N = 1e5 + 7;

struct Node{
	int p, s[2], mark;
	int v, tag, size;
	void init(int p1, int v1){
		p = p1, v = v1, size = 1;
	}
}tr[N];
int root, idx;
int n, q;

void pushdown(int x){
	if(tr[x].tag == 0)return;
	swap(tr[x].s[0], tr[x].s[1]);
	tr[tr[x].s[0]].tag ^= 1;
	tr[tr[x].s[1]].tag ^= 1;
	tr[x].tag = 0;
}

int get_k(int k){
	int x = root;
	while(1){
		pushdown(x);
		int y = tr[x].s[0];
		if(tr[y].size + 1 < k){
			k -= tr[y].size + 1;
			x = tr[x].s[1];
		}
		else if(tr[y].size >= k) x = y;
		else return x;
	}
}

void pushup(int x){
	tr[x].size = tr[tr[x].s[0]].size
		+ tr[tr[x].s[1]].size + 1;
}

void rotate(int x){
	int y = tr[x].p, z = tr[y].p;
	int k = tr[y].s[1] == x;
	tr[z].s[tr[z].s[1] == y] = x;
	tr[x].p = z, tr[y].p = x;
	tr[y].s[k] = tr[x].s[k ^ 1];
	tr[tr[x].s[k ^ 1]].p = y;
	tr[x].s[k ^ 1] = y;
	pushup(y), pushup(x);
}

void splay(int x, int k){
	while(tr[x].p != k){
		int y = tr[x].p, z = tr[y].p;
		if(z != k){
			(tr[y].s[0] == x) ^ (tr[z].s[0] == y)
				? rotate(y) : rotate(x);
		}
		rotate(x);
	}
	if(k == 0) root = x;
}

void insert(int v){
	int x = root, p = 0;
	while(x)p = x, x = tr[x].s[v > tr[x].v];
	x = ++ idx;
	tr[p].s[v > tr[p].v] = x;
	tr[x].init(p, v);
	splay(x, 0);
}

void output(int x){
	pushdown(x);
	if(tr[x].s[0]) output(tr[x].s[0]);
	if(tr[x].v >= 1 && tr[x].v <= n)
		printf("%d ", tr[x].v);
	if(tr[x].s[1]) output(tr[x].s[1]);
}

int main(){
	scanf("%d%d", &n, &q);
	insert(-1e6), insert(1e6);
	for(int i = 1;i <= n;i ++) insert(i);
	while(q --){
		int l, r;
		scanf("%d%d", &l, &r);
		l = get_k(l), r = get_k(r + 2);
		splay(l, 0), splay(r, l);
		tr[tr[r].s[0]].tag ^= 1;
	}
	output(root);
	return 0;
}