【BZOJ 3223】文艺平衡树 模板题

　　就是打个翻转标记，下推标记时记得交换左右孩子指针，查询kth和中序遍历输出时也记得要下推标记同时交换指针，二者不可缺！←这是易错点

仿陈竞潇学长模板的代码：

#include<cctype>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
struct node{
    node();
    node *ch[2],*fa;
    short reversal;
    short pl(){return this==fa->ch[1];}
    int d,sum;
    void push(); void count();
}*null;
int N,M;
node::node(){ch[0]=ch[1]=fa=null;reversal=sum=d=0;}
void node::push(){
    if (this==null) return;
    if (reversal==1){
        reversal=0;
        ch[0]->reversal^=1;
        ch[1]->reversal^=1;
        node *k=ch[0];
        ch[0]=ch[1];
        ch[1]=k;
    }
}
void node::count(){
    sum=ch[0]->sum+ch[1]->sum+1;
}
namespace Splay{
    node *ROOT;
    node *build(int l=1,int r=N){
        if (l>r) return null;
        int mid=(l+r)>>1;
        node *ro=new node;
        ro->d=mid;
        ro->ch[0]=build(l,mid-1);
        ro->ch[1]=build(mid+1,r);
        ro->ch[0]->fa=ro;
        ro->ch[1]->fa=ro;
        ro->count();
        return ro;
    }
    void Build(){
        null=new node;
        *null=node();
        ROOT=build();
        ROOT->count();
    }
    void rotate(node *k){
        node *r=k->fa; if (r==null||k==null) return;
        r->push(); k->push();
        int x=k->pl()^1;
        r->ch[x^1]=k->ch[x];
        r->ch[x^1]->fa=r;
        if (r->fa==null) ROOT=k;
        else r->fa->ch[r->pl()]=k;
        k->fa=r->fa;
        r->fa=k;
        k->ch[x]=r;
        r->count(); k->count();
    }
    void splay(node *r,node *tar=null){
        for (;r->fa!=tar;rotate(r))
         if (r->fa->fa!=tar)rotate(r->pl()==r->fa->pl()?r->fa:r);
        r->push();
    }
    node *kth(int x){
        node *r=ROOT;
        while (r!=null){
            r->push();
            if (r->ch[0]->sum>=x) r=r->ch[0];
            else if (r->ch[0]->sum+1>=x) return r;
            else x-=r->ch[0]->sum+1,r=r->ch[1];
        }return null;
    }
    void rollingover(int ll,int rr){
        node *ln=kth(ll-1),*rn=kth(rr+1),*r;
        if ((ln==null)&&(rn==null)) r=ROOT;
        else if (ln==null){
            splay(rn); r=ROOT->ch[0];
        }else if (rn==null){
            splay(ln); r=ROOT->ch[1];
        }else{
            splay(ln); splay(rn,ROOT);
            r=ROOT->ch[1]->ch[0];
        }r->reversal=r->reversal^1;
    }
    void AC(node *r=ROOT){
        if (r==null) return;
        r->push();
        AC(r->ch[0]);
        printf("%d ",r->d);
        AC(r->ch[1]);
    }
}
int getint()
{
    char c;
    while (!isdigit(c=getchar()));
    int a=c-'0';
    while (isdigit(c=getchar()))
     a=a*10+c-'0';
    return a;
}
int main()
{
    N=getint();M=getint();
    Splay::Build();
    while (M--){
        int l=getint(),r=getint();
        Splay::rollingover(l,r);
    }
    Splay::AC();
    return 0;
}

自己写的62行简洁代码：

#include<cstdio>
#include<algorithm>
#define read(x) x=getint()
using namespace std;
inline int getint(){char c;int ret=0;for(c=getchar();c<'0'||c>'9';c=getchar());for(;c>='0'&&c<='9';c=getchar())ret=ret*10+c-'0';return ret;}
struct node{
	node();
	node *fa,*ch[2];
	int d,sum;
	bool rev;
	bool pl() {return this->fa->ch[1]==this;}
	void setc(node *r,bool c) {r->fa=this; this->ch[c]=r;}
	void push() {if (rev){swap(ch[0],ch[1]);ch[0]->rev^=1;ch[1]->rev^=1;rev=0;}}
	void count() {sum=ch[0]->sum+ch[1]->sum+1;}
}*ROOT,*null;
node::node(){fa=ch[0]=ch[1]=null;d=sum=rev=0;}
int n,m;
inline node *build(int l,int r){
	if (l>r) return null; int mid=(l+r)>>1;	node *k=new node;
	k->ch[0]=build(l,mid-1); k->ch[1]=build(mid+1,r);
	if (k->ch[0]!=null) k->ch[0]->fa=k; if (k->ch[1]!=null) k->ch[1]->fa=k;
	k->d=mid; k->count(); return k;
}
inline void Build() {null=new node;*null=node();ROOT=build(1,n);}
inline void rotate(node *r){
	node *f=r->fa; bool c=r->pl();
	if (f!=ROOT) f->fa->setc(r,f->pl());
	else r->fa=null,ROOT=r;
	f->setc(r->ch[!c],c); r->setc(f,!c);
	f->count();
}
inline void update(node *r) {if (r!=null) update(r->fa); r->push();}
inline void splay(node *r,node *tar=null){
	update(r);
	for(;r->fa!=tar;rotate(r)) if (r->fa->fa!=tar) rotate(r->fa->pl()==r->pl()?r->fa:r);
	r->count();
}
inline node *kth(int x){
	if ((x==0)||(x==n+1)) return null;
	node *r=ROOT;
	while (1){
		r->push();
		if (r->ch[0]->sum>=x) r=r->ch[0];
		else if (r->ch[0]->sum+1>=x) return r;
		else {x-=r->ch[0]->sum+1; r=r->ch[1];}
	}
}
inline void reversal(int l,int r){
	node *ll=kth(l-1),*rr=kth(r+1);
	if ((ll==null)&&(rr==null)) ROOT->rev^=1;
	else if (ll==null) splay(rr),ROOT->ch[0]->rev^=1;
	else if (rr==null) splay(ll),ROOT->ch[1]->rev^=1;
	else splay(ll),splay(rr,ROOT),rr->ch[0]->rev^=1;
}
inline void AC(node *r) {if (r==null) return; r->push(); AC(r->ch[0]); printf("%d ",r->d); AC(r->ch[1]);}
int main(){
	read(n); read(m); Build();
	int l,r;
	while (m--) {read(l); read(r); reversal(l,r);}
	AC(ROOT);
	return 0;
}

然后就可以了