Submission #1253894

#	Time	Username	Problem	Language	Result	Execution time	Memory
1253894		Jer	Mountains (NOI20_mountains)	C++20	100 / 100	547 ms	107416 KiB

Mountains

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
const int MAXN = 3e5 + 5;

ll h[MAXN];
vector<ll> tree[4 * MAXN];
int n;

void build(int v, int l, int r) {
	if (l == r) return void(tree[v] = {h[l]});

	int m = (l + r) / 2;
	build(2 * v, l, m);
	build(2 * v + 1, m + 1, r);
	merge(tree[2 * v].begin(), tree[2 * v].end(),
		tree[2 * v + 1].begin(), tree[2 * v + 1].end(),
		back_inserter(tree[v]));
}

ll query(int v, int l, int r, int ql, int qr, ll val){
	if (qr < l or ql > r) return 0LL;
	if (ql <= l and qr >= r) 
		return (ll)(lower_bound(tree[v].begin(), tree[v].end(), val) - tree[v].begin());
	int m = (l + r) / 2;
	return query(2 * v, l, m, ql, qr, val) + query(2 * v + 1, m + 1, r, ql, qr, val);
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	cin >> n;
	for (int i = 0; i < n; i++) cin >> h[i];

	build(1, 0, n - 1);

	ll res = 0;
	for(int i = 1; i < n - 1; i++)
		res += (query(1, 0, n - 1, 0, i - 1, h[i])) * (query(1, 0, n - 1, i + 1, n - 1, h[i]));

	cout << res << '\n';

	return 0;
}

• Subtask 1: 2 / 2
• Subtask 2: 4 / 4
• Subtask 3: 9 / 9
• Subtask 4: 36 / 36
• Subtask 5: 28 / 28
• Subtask 6: 9 / 9
• Subtask 7: 12 / 12