Submission #1092254

#	Time	Username	Problem	Language	Result	Execution time	Memory
1092254		whoknow	Mountains (NOI20_mountains)	C++17	100 / 100	135 ms	9172 KiB

Mountains

#include <bits/stdc++.h>
#define ll long long
#define F first
#define S second
#define N 300005
#define ii pair<int,int>
#define bit(i,j) ((i>>j)&1)
#define sz(i) (int)i.size()
#define endl '\n'
using namespace std;
int n;
ll a[N];
namespace sub1
{
	ll res;
	int bit[N][2];
	void upd(int id,int v,int k)
	{
		for(id;id<=n;id+=(id&(-id)))
			bit[id][k]+=v;
	}
	int get(int id,int k)
	{
		int t=0;
		for(id;id>0;id-=((id&(-id))))
			t+=bit[id][k];
		return t;
	}
	void compress()
	{
		vector<ll>v;
		for(int i=1;i<=n;i++)
			v.push_back(a[i]);
		sort(v.begin(),v.end());
		v.resize(unique(v.begin(),v.end())-v.begin());
		for(int i=1;i<=n;i++)
			a[i]=lower_bound(v.begin(),v.end(),a[i])-v.begin()+1;
	}
	void solve()
	{
		compress();
		for(int i=2;i<=n;i++)
			upd(a[i],1,1);
		upd(a[1],1,0);
		for(int i=2;i<n;i++)
		{
			res+=1LL*get(a[i]-1,0)*get(a[i]-1,1);
			upd(a[i],-1,1);
			upd(a[i],1,0);
		}
		cout<<res;
	}
}
main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin>>n;
	for(int i=1;i<=n;i++)
		cin>>a[i];
	sub1::solve();
}

Compilation message (stderr)

Mountains.cpp: In function 'void sub1::upd(int, int, int)':
Mountains.cpp:19:7: warning: statement has no effect [-Wunused-value]
   19 |   for(id;id<=n;id+=(id&(-id)))
      |       ^~
Mountains.cpp: In function 'int sub1::get(int, int)':
Mountains.cpp:25:7: warning: statement has no effect [-Wunused-value]
   25 |   for(id;id>0;id-=((id&(-id))))
      |       ^~
Mountains.cpp: At global scope:
Mountains.cpp:54:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   54 | main()
      | ^~~~

• 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