Submission #210727

#	Time	Username	Problem	Language	Result	Execution time	Memory
210727		grt	Mountains (NOI20_mountains)	C++17	100 / 100	613 ms	26748 KiB

Mountains

#include <bits/stdc++.h>
#define PB push_back
#define ST first
#define ND second
#define _ ios_base::sync_with_stdio(0); cin.tie(0);
//mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());

using namespace std;

using ll = long long;
using pi = pair<int,int>;
using vi = vector<int>;

const int nax = 300*1000+10;
int n,nr;
ll h[nax];
map<ll,int>sc;
int T[(1<<20)],R;
int l[nax];

void update(int a,int x) {
	a+=R;
	T[a]+=x;
	while(a>1) {
		a/=2;
		T[a] = T[2*a]+T[2*a+1];
	}
}


int query(int a,int b) {
	a+=R; b+=R;
	if(a>b) return 0;
	int w = T[a]+(a!=b?T[b]:0);
	while(a/2!=b/2) {
		if(a%2==0) w+=T[a+1];
		if(b%2==1) w+=T[b-1];
		a/=2;
		b/=2;
	}
	return w;
}

ll ans;

int main() {_
	cin>>n;
	for(int i=1; i<=n; i++) {
		cin>>h[i];
		sc[h[i]];
	}
	for(auto &it:sc) it.ND = nr++;
	R=1;
	while(R<nr) R*=2;
	for(int i=1; i<=n; i++) h[i] = sc[h[i]];
	for(int i=1; i<=n; i++) {
		l[i] = query(0,h[i]-1);
		update(h[i],1);
	}
	for(int i=1; i<2*R; i++) T[i] = 0;
	for(int i=n; i>=1; i--) {
		int x = query(0,h[i]-1);
		update(h[i],1);
		ans += (ll)l[i]*x;
	}
	cout<<ans;
	
}

• 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