Luogu P3391 [template] literary balanced tree Splay balanced tree

https://www.luogu.org/problemnew/show/P3391

Getting the title written explanations before rewriting training board. wdnmd to true '==' written '=' no compiler error chant.

#include<bits/stdc++.h>
using namespace std;
const int maxn=100010;
int n,m,rt=0,c[maxn][2]={},fa[maxn]={},rev[maxn]={},siz[maxn]={};
inline void pushup(int x){ 
	siz[x]=siz[c[x][0]]+siz[c[x][1]]+1;
}
void pushdown(int x){
	if(rev[x]){ 
		swap(c[x][0],c[x][1]);
		rev[c[x][0]]^=1; rev[c[x][1]]^=1; rev[x]=0; 
	}
}
void build(int x,int l,int r){
	if(l>r)return;
	if(l==r){
		fa[l]=x;siz[l]=1;
		if(l<x)c[x][0]=l;
		else c[x][1]=l;
		return;
	}
	int mid=(l+r)/2;
	build(mid,l,mid-1);build(mid,mid+1,r);
	if(mid<x)c[x][0]=mid;
	else c[x][1]=mid;
	fa[mid]=x;pushup(mid);
}
void rot(int x,int &k){
	int pa=fa[x],gpa,l,r;gpa=fa[pa];
	if(x==c[pa][0])l=0;
	else l=1; r=l^1;
	if(pa!=k){
		if(c[gpa][0]==pa)c[gpa][0]=x;
		else c[gpa][1]=x;
	}else k=x;
	fa[x]=gpa;fa[pa]=x;fa[c[x][r]]=pa;
	c[pa][l]=c[x][r];c[x][r]=pa;
	pushup(pa); pushup(x);
}
/*void dfs(int x){
	if(x==0)return;
	cout<<x<<c[x][0]<<c[x][1]<<endl;
	dfs(c[x][0]);
	dfs(c[x][1]);
}*/
void splay(int x,int &k){
	while(x!=k){
		int pa=fa[x];int gpa=fa[pa];
		if(pa!=k){
			if((c[gpa][1]==pa)^(c[pa][1]==x))rot(x,k);
			else rot(pa,k);
		}rot(x,k);
		//dfs(rt);cout<<endl;
	}
}
int find(int v,int x){
	pushdown(x);
	if(v==siz[c[x][0]]+1)return x;
	else if(v<siz[c[x][0]]+1) return find(v,c[x][0]);
	else return find(v-siz[c[x][0]]-1,c[x][1]);
}
void mrev(int l,int r){
	int x=find(l,rt),y=find(r+2,rt);
	//cout<<x<<y<<endl;
	splay(x,rt);splay(y,c[x][1]);
	//cout<<siz[y]<<endl;
	rev[c[y][0]]^=1;
}
int main(){
	scanf("%d%d",&n,&m);
	build(0,1,n+2);rt=(3+n)/2;
	for(int i=1;i<=m;++i){
		int x,y;
		scanf("%d%d",&x,&y);
		if(x!=y)mrev(x,y);
	}
	for(int i=1;i<=n;++i){
		printf("%d ",find(i+1,rt)-1);
	}cout<<endl;
	return 0;
}