Submission #224562

#	Time	Username	Problem	Language	Result	Execution time	Memory
224562		Berted	Mountains (NOI20_mountains)	C++14	100 / 100	135 ms	8808 KiB

Mountains

#include <iostream>
#include <vector>
#include <algorithm>
#define ll long long
#define pii pair<ll, int>
#define fst first
#define snd second
using namespace std;
int n, fenwick[300001] = {};
vector<pii> dt;
ll to = 0;
int query(int x)
{
	int to = 0;
	for (; x; x -= x & (-x)) {to += fenwick[x];}
	return to;
}
void upd(int x)
{
	for (; x <= n; x += x & (-x)) {fenwick[x]++;}
}
int main()
{
	ios :: sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> n;
	for (int i = 0; i < n; i++) {ll x; cin >> x; dt.push_back({x, i + 1});}
	sort(dt.begin(), dt.end());
	int i = 0;
	while (i < n)
	{
		to += (ll)query(dt[i].snd) * (i - query(dt[i].snd));
		int j = i + 1;
		for (; j < n && dt[j].fst == dt[j - 1].fst; j++) {to += (ll)query(dt[j].snd) * (i - query(dt[j].snd));}
		for (; i < j; i++) {upd(dt[i].snd);}
	}
	cout << to << "\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