splay 模板

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cstring>
#include <cmath>
using namespace std;
#define rt ch[root][1]
#define lrt ch[rt][0]
#define ls ch[x][0]
#define rs ch[x][1]
#define inf 0x7fffffff
const int maxn=500100;

int root,top;//root为新建节点时的根节点
int ch[maxn][2],f[maxn];
long long sz[maxn],num[maxn],val[maxn],sum[maxn],add[maxn];
int n,m;

//ch[x][0],ch[x][1]:x的左右儿子,f[x]:x的父亲节点,val[x]:x的值,sz[x]以x为根的子树的节点个数
inline void pushup(int x)
{
    sz[x]=sz[ls]+sz[rs]+1;
    sum[x]=sum[ls]+sum[rs]+val[x];
    //维护其他信息
}
inline void pushdown(int x)
{
    if(add[x])
    {
        val[x]+=add[x];
        add[ls]+=add[x];
        add[rs]+=add[x];
        sum[ls]+=(long long)(sz[ls]*add[x]);
        sum[rs]+=(long long)(sz[rs]*add[x]);
        add[x]=0;
    }
    //维护其他信息
}

inline void link(int y,int x,int d)
//把节点y的(左或右)儿子设为x
{
    f[x]=y;
    ch[y][d]=x;
}

inline int is(int x)
//判断x为左儿子0还是右儿子1
{
    return ch[f[x]][1]==x;
}

inline void rotate(int x,int d)
{
    int y=f[x];
    int z=f[y];
    pushdown(y);
    pushdown(x);
    link(y,ch[x][d],!d);
    if(z) link(z,x,is(y));
    f[x]=z;
    link(x,y,d);
    pushup(y);
}
inline void zag(int x)
{
    rotate(x,0);
}
inline void zig(int x)
{
    rotate(x,1);
}
inline void splay(int x,int goal=0)//第二个元素没有传参就默认为0，splay到0即将该节点旋转到根
//将根为r的子树调整到x的父节点为goal的位置
{
    pushdown(x);

    while(f[x]!=goal)
    {
        int y=f[x];
        int z=f[y];
        if(z==goal)
        {
            rotate(x,!is(x));
            break;
        }
        if(ch[z][0]==y)
        {
            if(ch[y][0]==x) zig(y),zig(x);
            else zag(x),zig(x);
        }
        else
        {
            if(ch[y][1]==x) zag(y),zag(x);
            else zig(x),zag(x);
        }
    }
    if(goal==0) root=x;
    pushup(x);
}
inline int pre(int x)//获得前驱,调用时pre(root)即可
{
    x=ls;
    if(x==0) return inf;
    while(rs) x=rs;
    return val[x];
}


inline int next(int x)//调用时next(root)即可，后继
{
    x=rs;
    if(x==0) return inf;
    while(ls) x=ls;
    return val[x];
}

//splay操作一般不做改动
inline void newnode(int &x,int father,long long v)
{
    x=++top;
    f[x]=father;
    val[x]=v;
    add[x]=0;
    ls=rs=0;
    sz[x]=0;

    //.....按题意建立信息
}
inline bool insert(int v)
{
    int x=root;
    while(ch[x][val[x]<v])
    {
        if(val[x]==v)
        {
            splay(x);
            return false;
        }
        x=ch[x][val[x]<v];
    }
    newnode(ch[x][val[x]<v],x,v);
    splay(ch[x][val[x]<v]);
    return true;
}

inline void build(int &x,int y,int l,int r)
{
    if(l>r) return ;
    int mid=(l+r)>>1;
    newnode(x,y,num[mid]);
    build(ls,x,l,mid-1);
    build(rs,x,mid+1,r);
    pushup(x);

}

inline void init(int n)
{
    root=top=0;
    ch[0][0]=ch[0][1]=f[0]=val[0]=add[0]=sz[0]=sum[0]=0;
    newnode(root,0,-inf);
    newnode(rt,root,inf);
    sz[root]=2;
    int vv,ans=0;
    pushup(rt);
    pushup(root);
    scanf("%d",&vv);
    insert(vv);
    ans=vv;

    for(int i=2;i<=n;i++){
        if(scanf("%d",&vv)==-1) vv=0;
//        scanf("%d",&vv);
        if(insert(vv)){
            ans+=min(fabs(pre(root)-vv), fabs(next(root)-vv));
        }
    }




    cout<<ans<<endl;
    //for(int x=0;x<=top;x++){
    //    printf("x=%d f[x]=%d ls=%d rs=%d val=%d sum=%d add=%d sz=%d\n",x,f[x],ls,rs,val[x],sum[x],add[x],sz[x]);
    //}
}


inline int get_k(int x,int k)//返回的是第k小的点的标号(从小到大)，值要用val来获取
{
    pushdown(x);
    int num=sz[ls]+1;
    if(num==k) return x;
    if(k<num) return get_k(ls,k);
    return get_k(rs,k-num);
}

inline void update()
{
    int l,r;
    long long c;
    scanf("%d %d %lld",&l,&r,&c);
    int x=get_k(root,l);
    splay(x);
    int y=get_k(root,r+2);
    splay(y,root);
    add[lrt]+=c;
    sum[lrt]+=sz[lrt]*c;
}
//查询一段区间的值
inline void query()
{
    int l,r;
    scanf("%d%d",&l,&r);
    int x,y;
    x=get_k(root,l);
    y=get_k(root,r+2);
    splay(x);
    splay(y,root);
    printf("%lld\n",sum[lrt]);
}


int main(){
    scanf("%d",&n);
    init(n);
}