Submission #1173759

#	Time	Username	Problem	Language	Result	Execution time	Memory
1173759		ezzzay	Mountains (NOI20_mountains)	C++20	100 / 100	339 ms	26300 KiB

Mountains

#include<bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
#define pb push_back
#define int long long
const int N=4e5;
int a[N];
int ps[N];
int sf[N];
void upps(int idx, int val){
    while(idx<N){
        ps[idx]+=val;
        idx+= idx & -idx;
    }
}
void upsf(int idx, int val){
    while(idx<N){
        sf[idx]+=val;
        idx+= idx & -idx;
    }
}
int fnsf(int idx){
    int s=0;
    while(idx>0){
        s+=sf[idx];
        idx-= idx &-idx;
    }
    return s;
}
int fnps(int idx){
    int s=0;
    while(idx>0){
        s+=ps[idx];
        idx-= idx &-idx;
    }
    return s;
}
signed main(){
    int n;
    cin>>n;
    map<int,int>mp;
    for(int i=1;i<=n;i++){
        cin>>a[i];
        mp[a[i]];
    }
    int id=2;
    for(auto it=mp.begin();it!=mp.end();it++){
        it->ss = id++;
    }
    for(int i=1;i<=n;i++)a[i]=mp[a[i]];
    for(int i=1;i<=n;i++){
        upsf(a[i],1);
    }
    int ans=0;
    for(int i=1;i<=n;i++){
        ans+= ( fnsf(a[i]-1)) *((fnps(a[i]-1)));
       // cout<<(fnsf(N-1) - fnsf(a[i])) << " "<<(fnps(N-1)-(fnps(a[i])))<<endl;
        upsf(a[i],-1);
        upps(a[i],1);
    }
    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