BZOJ 4764: 弹飞大爷

#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
//by NeighThorn
using namespace std;

const int maxn=200000+5;

int n,m,p[maxn];

struct M{
	
	int dis;
	bool reverse;
	M *cf,*son[2],*father;
	
	inline M(void){
		dis=1;
		cf=NULL;
		father=NULL;
		reverse=false;
		son[1]=son[0]=NULL;
	}
	
	inline void update(void){
		dis=1;
		if(son[0]) dis+=son[0]->dis;
		if(son[1]) dis+=son[1]->dis;
	}
	
	inline bool isroot(void){
		if(father==NULL)
			return true;
		if(father->son[0]==this)
			return false;
		if(father->son[1]==this)
			return false;
		return true;
	}
	
	inline void pushdown(void){
		if(reverse){
			reverse=false;
			swap(son[0],son[1]);
			if(son[0]) son[0]->reverse^=true;
			if(son[1]) son[1]->reverse^=true;
		}
	}
	
}tr[maxn];

inline void connect(M *f,M *t,int s){
	if(t!=NULL) t->father=f;
	if(f!=NULL) f->son[s]=t;
}

inline void rotate(M *t){
	M *f=t->father;
	M *g=f->father;
	int s=(f->son[1]==t);
	connect(f,t->son[!s],s);
	connect(t,f,!s);
	t->father=g;
	if(g&&g->son[0]==f) g->son[0]=t;
	if(g&&g->son[1]==f) g->son[1]=t;
	f->update();t->update();
}

inline void push(M *t){
	static M *stk[maxn];
	int top=0;
	stk[top++]=t;
	while(!t->isroot())
		stk[top++]=t=t->father;
	while(top) stk[--top]->pushdown();
}

inline void splay(M *t){
	push(t);
	while(!t->isroot()){
		M *f=t->father;
		M *g=f->father;
		if(f->isroot())
			rotate(t);
		else{
			bool a=(f&&f->son[1]==t);
			bool b=(g&&g->son[1]==f);
			if(a==b)
				rotate(f),rotate(t);
			else
				rotate(t),rotate(t);
		}
	}
}

inline void access(M *t){
	M *p=NULL;
	while(t!=NULL){
		splay(t);
		t->son[1]=p,t->update();
		p=t,t=t->father;
	}
}

inline void makeroot(M *t){
	access(t);splay(t);t->reverse^=true;
}

inline void cut(M *t){
	access(t);splay(t);
	if(t->son[0]) t->son[0]->father=NULL;
	if(t->son[1]) t->son[1]->father=NULL;
	t->son[0]=t->son[1]=NULL;t->update();
}

inline void link(M *f,M *t){
	makeroot(t);t->father=f;
}

inline M *find(M *t){
	access(t);
	splay(t);
	M *r=t;
	while(r->son[0])
		r=r->son[0];
	return r;
}

inline void add(M *t,M *f){
	if(t==f)
		t->cf=f;
	else if(find(t)!=find(f))
		link(f,t);
	else
		makeroot(t),t->cf=f;
}

inline void change(M *t,M *f){
	M *r=find(t);
	if(r->cf==NULL)
		cut(t),add(t,f);
	else{
		if(r==t)
			t->cf=NULL,add(t,f);
		else{
			M *cir=r->cf;
			cut(t);add(t,f);
			if(find(r)!=find(cir))
				r->cf=NULL,link(cir,r);
		}
	}
}

signed main(void){
	scanf("%d%d",&n,&m);
	for(int i=0;i<=n;i++)
		tr[i]=M();
	for(int i=1;i<=n;i++)
		scanf("%d",&p[i]),p[i]+=i,add(tr+i,tr+(((p[i]>n)||(p[i]<1))?0:p[i]));
	for(int q=1,opt,x,y;q<=m;q++){
		scanf("%d",&opt);
		if(opt==1){
			scanf("%d",&x);
			M *r=find(tr+x);
			if(r->cf==NULL)
				makeroot(tr+0),access(tr+x),splay(tr+x),printf("%d\n",tr[x].dis-1);
			else
				puts("-1");
		}
		else{
			scanf("%d%d",&x,&y);p[x]=y+x;
			change(tr+x,tr+(((p[x]>n)||(p[x]<1))?0:p[x]));
		}
	}
	return 0;
}