Submission #226363

#	Time	Username	Problem	Language	Result	Execution time	Memory
226363		ezdp	Mountains (NOI20_mountains)	C++14	100 / 100	192 ms	17784 KiB

Mountains

/**
link: https://oj.uz/problem/view/NOI20_mountains
*/
#include<bits/stdc++.h>
#define endl '\n'
#define pb push_back
#define fr first
#define sc second
#define ll long long int
#define bit(idx) idx&(-idx)
#define bin(x, a) bitset<a>(x)
#define all(A) A.begin(), A.end()
#define debug(x) cout << #x << " = " << x << endl;
using namespace std;

const int MAXN = 3e5 + 5;

ll n, A[MAXN], BIT[MAXN], tmp[MAXN], sz;

void upd(int idx){
	for(int _idx = idx + 1; _idx < MAXN; _idx += bit(_idx)){
		++ BIT[_idx];
	}
}

ll qry(int idx){
	ll ret = 0;
	for(int _idx = idx + 1; _idx > 0; _idx -= bit(_idx)){
		ret += BIT[_idx];
	}
	return ret;
}

int main(){
	ios_base::sync_with_stdio(NULL); cin.tie(); cout.tie();
	cin >> n;
	for(int i = 0; i < n; i ++){
		cin >> A[i];
		tmp[sz ++] = A[i];
	}
	sort(tmp, tmp + sz);
	sz = unique(tmp, tmp + sz) - tmp;
	for(int i = 0; i < n; i ++)
		A[i] = lower_bound(tmp, tmp + sz, A[i]) - tmp;
	ll L[MAXN] = {0}, R[MAXN] = {0};
	for(int i = 0; i < n; i ++){
		L[i] = qry(A[i] - 1);
		upd(A[i]);
	}
	memset(BIT, 0, sizeof(BIT));
	for(int i = n - 1; i >= 0; i --){
		R[i] = qry(A[i] - 1);
		upd(A[i]);
	}
	/// cout << "A: "; for(int i = 0; i < n; i ++) cout << A[i] << " "; cout << endl;
	/// cout << "L: "; for(int i = 0; i < n; i ++) cout << L[i] << " "; cout << endl;
	/// cout << "R: "; for(int i = 0; i < n; i ++) cout << R[i] << " "; cout << endl;
	ll ans = 0;
	for(int i = 0; i < n; i ++)
		ans += L[i] * R[i];
	cout << ans << endl;
}
/**
5
0 1 1 0 1

2

6
500 20 900 0 900 70

7
*/

• 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