Submission #287122

#	Time	Username	Problem	Language	Result	Execution time	Memory
287122		sabamaku	Mountains (NOI20_mountains)	C++14	100 / 100	1494 ms	34332 KiB

Mountains

#include<bits/stdc++.h>
using namespace std;

long long n,x,p[3][300005],ans,d[300005],sum,sum1,s[300005];

map <long long,int> mp;

void update(int a){
    for(int i = a; i <= n; i += (i & -i)){
        p[x][i]++;
    }
}

void deleteit(int a){
    for(int i = a; i <= n; i += (i & -i)){
        p[1][i]--;
    }
}

void solve(int a){
    sum = 0;
    for(int i = a - 1; i >= 1; i -= (i & -i)){
        sum += p[x][i];
    }
}

int main(){
    cin >> n;
    for(int i = 1; i <= n; i++){
        cin >> d[i];
        s[i] = d[i];
    }
    sort(s + 1, s + n + 1);
    for(int i = 1; i <= n; i++){
        if(mp[s[i]] == 0){
            x++;
            mp[s[i]] = x; 
        }
    }
    x = 1;
    for(int i = n; i >= 2; i--){
        update(mp[d[i]]);
    }
    for(int i = 2; i < n; i++){
        deleteit(mp[d[i]]);
        x = 0;
        update(mp[d[i - 1]]);
        x = 1;
        solve(mp[d[i]]);
        sum1 = sum;
        x = 0;
        solve(mp[d[i]]);
        ans += sum * sum1;
        //cout << sum << " " << sum1 << " " << mp[d[i]] << endl;
    }
    cout << ans << endl;
}

• 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