제출 #540994

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
540994		bayemirov	Mountains (NOI20_mountains)	C++17	0 / 100	738 ms	40176 KiB

Mountains

// bayemirov

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <bits/stdc++.h>

using namespace __gnu_pbds;
using namespace std;


typedef long long ll;

typedef tree<
ll,
null_type,
less_equal<ll>,
rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;

const int N = 4e5;

int n;
ll h[N], ans;
ordered_set a, b;

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> h[i];
		if (i > 1)
			b.insert(h[i]);
	}
	a.insert(h[0]);
	for (int i = 1; i < n; i++) {
		int cnt_x = a.order_of_key(h[i]);
		int cnt_z = b.order_of_key(h[i]);
		//cout << i << ' ' << cnt_x << ' ' << cnt_z << "\n";
		ans += cnt_x*1ll*cnt_z;
		a.insert(h[i]);
		b.erase(b.find_by_order(h[i+1]));
	}
	cout << ans;
	return 0;
}

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