Bzoj-营业额统计 Set||treap

#include<cstdio>
#include<cmath>
#include<cstring>
#include<iostream>
#include<map>
#include<set>
#include<queue> 
#include<algorithm>
using namespace std;
#define INF 0x7FFFFFFF
#define ll long long
void read(int &x){
    x=0;int 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();}
    x*=f;
}
set<int>tree;
int n,x,ans,add;
int main(){
	read(n);tree.clear();read(x);ans=x;tree.insert(x);
	for(int i=2;i<=n;i++){
		read(x);add=INF;
		set<int>::iterator a=--tree.lower_bound(x),b=tree.lower_bound(x);
		if(tree.count(*a)) add=min(add,abs(x-*a));
		if(tree.count(*b)) add=min(add,abs(x-*b));
		//printf("%d %d\n",*a,*b);
		ans+=add;
		tree.insert(x);
	}
	printf("%d\n",ans);
	return 0;
}