Submission #798586

#	Time	Username	Problem	Language	Result	Execution time	Memory
798586		AndiR	Mountains (NOI20_mountains)	C++14	100 / 100	770 ms	44592 KiB

Mountains

#include <iostream>
#include <set>
#include <map>

using namespace std;
typedef long long ll;
const int Nmax=300000;

ll n, v[Nmax];
set <ll> s;
map <ll, int> m;
int aib[Nmax+5];
ll sol[Nmax];
void aib_add(int pos){
    for (int i=pos; i<=n; i+=i&-i)
        aib[i]++;
}
int aib_check(int pos){
    int r=0;
    for (int i=pos; i>0; i-=i&-i)
        r+=aib[i];
    return r;
}
int main()
{
    cin>>n;
    for (int i=0; i<n; i++){
        cin>>v[i];
        s.insert(v[i]);
    }
    int ind=1;
    for (auto it=s.begin(); it!=s.end(); it++)
        m[*it]=ind++;
    for (int i=0; i<n; i++){
        aib_add(m[v[i]]);
        sol[i]=aib_check(m[v[i]]-1);
    }
    for (int i=0; i<=n; i++)
        aib[i]=0;
    ll t=0;
    for (int i=n-1; i>=0; i--){
        aib_add(m[v[i]]);
        t+=sol[i]*aib_check(m[v[i]]-1);
    }
    cout<<t;
    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