调了一下午 + 一晚上，人麻了。

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

const int N = 1e5 + 10;
const int INF = 1e9 + 42;
int n, m, a[N];
int tot, rt, fa[N], tag[N], son[N][2], sz[N], val[N], rev[N];

int newnode(int v, int p){
	++tot;
	val[tot] = v, sz[tot] = 1, fa[tot] = p;
	return tot;
}

bool side(int u, int p){
	return (son[p][1] == u);
}

void pushup(int u){
	sz[u] = sz[son[u][0]] + sz[son[u][1]] + 1;
}

void pushdown(int u){
	if(tag[u]){
		tag[son[u][0]] ^= 1, tag[son[u][1]] ^= 1;
		swap(son[u][0], son[u][1]);
		tag[u] = 0;
	}
}

void rotate(int u){
	int p = fa[u], g = fa[p];
	int d = side(u, p);
//	pushdown(g), pushdown(p), pushdown(u); 
	son[p][d] = son[u][!d], fa[son[u][!d]] = p;
	fa[u] = g;
	if(g)
		son[g][side(p, g)] = u;
	son[u][!d] = p, fa[p] = u;
	pushup(p), pushup(u);
}

void splay(int x, int y){
	while(fa[x] != y){
		int p = fa[x], g = fa[p];
		if(g != y && side(x, p) == side(p, g))
			rotate(p);
		rotate(x);
	}
	if(!y)
		rt = x;
}

void insert(int &u, int v, int p){
	if(!u){
		u = newnode(v, p);
		splay(u, 0);
		return ;
	}
	if(v < val[u])
		insert(son[u][0], v, u);
	if(v > val[u])
		insert(son[u][1], v, u);
	pushup(u);
}

int kth(int u, int k){
	if(sz[son[u][0]] + 1 == k)
		return u;
	if(k <= sz[son[u][0]])
		return kth(son[u][0], k);
	return kth(son[u][1], k - sz[son[u][0]] - 1);
}

void reverse(int l, int r){
	l = kth(rt, l), r = kth(rt, r + 2);
	splay(l, 0);
	splay(r, l);
	int u = son[son[rt][1]][0];//根的左儿子的右儿子的子树就是 [l, r] 
	tag[u] ^= 1;
}

void dfs(int u){
	pushdown(u);
	if(son[u][0])
		dfs(son[u][0]);
	if(val[u] > 1 && val[u] < n + 2)
		printf("%d ", val[u] - 1);
	if(son[u][1])
		dfs(son[u][1]);
}

int main(){
	scanf("%d%d", &n, &m);
	rt = 0;
//	insert(rt, -INF, 0);
	for(int i=1;i<=n+2;i++)
		insert(rt, i, 0);
//	insert(rt, INF, 0);
	while(m--){
		int l, r;
		scanf("%d%d", &l, &r);
		reverse(l, r);
	}
	dfs(rt);
	return 0;
}