rt. CE

类 "tree<int,null_type>" 没有成员 "find_by_order"

#include <bits/extc++.h>
using namespace __gnu_pbds;
using namespace __gnu_cxx;
using namespace std;
tree<int, null_type> phs;
int n, a, ans;
signed main()
{
	cin >> n >> a;
	phs.insert(a);
	ans = a;
	for (int i = 1; i < n; i++)
	{
		cin >> a;
		if (phs.order_of_key(a) == i)
			ans += a - *phs.find_by_order(i - 1);
		else
			ans += *phs.lower_bound(a) - a;
		phs.insert(a);
	}
	cout << ans << endl;
	return 0;
}