Submission #329151

#	Time	Username	Problem	Language	Result	Execution time	Memory
329151		poom2904	Mountains (NOI20_mountains)	C++11	100 / 100	149 ms	13548 KiB

Mountains

#include <bits/stdc++.h>
using namespace std;
using ll = long long int;
int n;
bool cmp(const pair<ll,int> a,const pair<ll,int> b)
{
    return a.first<b.first;
}
vector<int> new_hei(300001,0);
vector<ll> lower_l(300001,0);
vector<ll> lower_r(300001,0);
vector<ll> fen(300001);
void upd(int idx)
{
    for(;idx<=300000;idx+=idx&-idx)fen[idx]++;
}
ll read(int idx)
{
    ll res=0;
    for(;idx>0;idx-=idx&-idx)res+=fen[idx];
    return res;
}
int main()
{
    ios_base::sync_with_stdio(false);cin.tie(0);
    cin>>n;
    vector<pair<ll,int> > height(n);
    for(int i=0;i<n;i++){cin>>height[i].first;height[i].second=i+1;}
    sort(height.begin(),height.end(),cmp);
    ll pre=-1,new_h=0;
    for(int i=0;i<n;)
    {
        if(height[i].first!=pre)
        {
            new_h++;
            pre=height[i].first;
        }
        new_hei[height[i++].second]=new_h;
    }
    fill(fen.begin(),fen.end(),0);
    for(int i=2;i<=n;i++)
    {
        upd(new_hei[i-1]);
        lower_l[i]=read(new_hei[i]-1);
    }
    fill(fen.begin(),fen.end(),0);
    for(int i=n-1;i>=1;i--)
    {
        upd(new_hei[i+1]);
        lower_r[i]=read(new_hei[i]-1);
    }
    ll res=0;
    for(int i=1;i<=n;i++)res+=lower_l[i]*lower_r[i];
    cout<<res;
    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