学步园

#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
using namespace std;
#define inf 1000000000
inline int read(){
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
const int maxn=50001;
int n,ans,sz,rt,t1,t2,c[maxn][2],fa[maxn],num[maxn];
inline void rotate(int x,int &k){
	int y=fa[x],z=fa[y],l,r;
	if(c[y][0]==x)l=0;else l=1;r=l^1;
	if(y==k)k=x;
	else{
		if(c[z][0]==y)c[z][0]=x;
		else c[z][1]=x;
	}
	fa[x]=z;fa[y]=x;fa[c[x][r]]=y;
	c[y][l]=c[x][r];c[x][r]=y;
}
inline void splay(int x,int &k){
	int y,z;
	while(x!=k){
		y=fa[x];z=fa[y];
		if(y!=k){
			if((c[y][0]==x)^(c[z][0]==y))rotate(x,k);
			else rotate(y,k);
		}
		rotate(x,k);
	}
}
inline void ins(int &k,int x,int last){
	if(!k){num[k=++sz]=x;fa[k]=last;splay(k,rt);return;}
	if(x<num[k])ins(c[k][0],x,k);
	else ins(c[k][1],x,k);
}
inline void ask_prev(int k,int x)
{
	if(!k)return;
	if(num[k]<=x){t1=num[k];ask_prev(c[k][1],x);}
	else ask_prev(c[k][0],x);
}
inline void ask_succ(int k,int x){
	if(!k)return;
	if(num[k]>=x){t2=num[k];ask_succ(c[k][0],x);}
	else ask_succ(c[k][1],x);
}
int main(){
	n=read();
	for(int i=1;i<=n;i++){
		int x;if(scanf("%d",&x)==EOF)x=0;
		t1=-inf;t2=inf;
		ask_prev(rt,x);ask_succ(rt,x);
		if(i!=1)ans+=min(x-t1,t2-x);
		else ans+=x;
		ins(rt,x,0);
	}
	printf("%d",ans);
	return 0;
}

4.20 * 1 (Treap)

#include<iostream>
#include<cstdlib>
#include<cstdio>
#include<ctime>
#define inf 1000000000
using namespace std;
struct data{
	int l,r,num,rnd;
}tr[50001];
int n,size,root,ans1,ans2,ans;
void lturn(int &k){
	int t=tr[k].r;
	tr[k].r=tr[t].l;
	tr[t].l=k;
	k=t;
}
void rturn(int &k){
	int t=tr[k].l;
	tr[k].l=tr[t].r;
	tr[t].r=k;
	k=t;
}
void insert(int &k,int x){
	if(k==0){
		k=++size;
		tr[k].num=x;
		tr[k].rnd=rand();
		return;
	}
	if(x<tr[k].num){
		insert(tr[k].l,x);
		if(tr[tr[k].l].rnd<tr[k].rnd)rturn(k);
	}
	else if(x>tr[k].num){
		insert(tr[k].r,x);
		if(tr[tr[k].r].rnd<tr[k].rnd)lturn(k);
	}
}
void ask_before(int k,int x){
	if(k==0)return;
	else if(x>=tr[k].num){ans1=tr[k].num;ask_before(tr[k].r,x);}
	else ask_before(tr[k].l,x);
}
void ask_after(int k,int x){
	
	if(k==0)return;
	else if(x<=tr[k].num){ans2=tr[k].num;ask_after(tr[k].l,x);}
	else ask_after(tr[k].r,x);
}
int main(){
	scanf("%d",&n);int t;
	for(int i=1;i<=n;i++){
		if(scanf("%d",&t)==EOF)t=0;
		ans1=-inf;ans2=inf;
		ask_before(root,t);
		ask_after(root,t);
		if(i!=1)ans+=min(t-ans1,ans2-t);
		else ans+=t;
		insert(root,t);
	}
	printf("%d",ans);
	return 0;
}

7.28 * 1 (Splay)