Submission #210548

#	Time	Username	Problem	Language	Result	Execution time	Memory
210548		mayhoubsaleh	Mountains (NOI20_mountains)	C++14	100 / 100	560 ms	26232 KiB

Mountains

#include <bits/stdc++.h>
#include <string>
#define ll long long
#define pb push_back
#define IOS ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);


using namespace std;
map<ll,ll>m;
ll ans;
const ll maxn=3e5+100;
ll n,a[maxn];
ll tr[maxn],lft[maxn];
ll cnt=1;
ll sum(ll id){
    ll ret=0;
    for(;id;id-=id&(-id))ret+=tr[id];
    return ret;
}

void add(ll id){
    for(;id<=cnt;id+=id&(-id))tr[id]++;
}
ll qur(ll l,ll r){
    if(r==0)return 0;
    return sum(r)-sum(l-1);
}
int main()
{
    IOS
    cin>>n;
    for(ll i=0;i<n;i++){
        cin>>a[i];
        m[a[i]]=1;
    }

    for(auto &x:m){
        x.second=cnt++;
    }
    for(ll i=0;i<n;i++){
        a[i]=m[a[i]];
        //cout<<a[i]<<' ';
    }
    cnt--;
    for(ll i=0;i<n;i++){
        lft[i]=qur(1,a[i]-1);
        add(a[i]);
        //cout<<lft[i]<<' ';
    }

    for(ll i=0;i<n;i++){
        ll righ=qur(1,a[i]-1)-lft[i];
        ans+=righ*lft[i];
    }
    cout<<ans<<endl;
    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