纯粹的Treap,但未果，求助！TAT

#include<bits/stdc++.h>
using namespace std;
const int N = 5e5+5;
int n,k,ans(0),rt,w(0);
struct node{
	int lc,rc,fa,pos,vis;
	#define lc(x) t[x].lc
	#define rc(x) t[x].rc
	#define fa(x) t[x].fa
	#define pos(x) t[x].pos
	#define vis(x) t[x].vis
}t[N];
void zig(int &x){ //右旋 
	int y=lc(x);
	lc(x) = rc(y);
	rc(y) = x;
	x = y;
} 
void zag(int &x){ //左旋 
	int y=rc(x);
	rc(x) = lc(y);
	lc(y) = x;
	x = y;
}
void insert(int &x,const int vi){
	if (!x){
		vis(x=++w)=vi;
		pos(x)=rand();
		return ;
	}
	if (vi<vis(x)){
		insert(lc(x),vi);
		if (pos(lc(x))<pos(x))
			zig(x);
	}
	else{
		insert(lc(x),vi);
		if (pos(lc(x))<pos(x))
			zag(x);
	}
}
int querypre(const int vi){
	int x=rt,pr=-INT_MAX;
	while(x){
		if (vi>=vis(x)) pr=vis(x),x=rc(x);
		else x=lc(x);
	}
	return pr;
}
int querysuf(const int vi){
	int x=rt,sf=INT_MAX;
	while(x){
		if (vi<=vis(x)) sf=vis(x),x=lc(x);
		else x=rc(x); 
	}
	return sf;
}
int main(){
	cin >> n >> k;
	insert(rt,k);
	ans+=k;
	for (int i=2;i<=n;i++){
		cin >> k;
		int x=querypre(k);
		int y=querysuf(k);
		ans += min(k-x,y-k);
		insert(rt,k);
	}
	cout << ans;
	return 0;
}