Submission #285689

#	Time	Username	Problem	Language	Result	Execution time	Memory
285689		NintsiChkhaidze	Mountains (NOI20_mountains)	C++14	100 / 100	513 ms	16248 KiB

Mountains

#include <bits/stdc++.h>
#define fast ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define pb push_back
#define f first
#define s second
#define ll long long
#define int long long
#define mod 1000000007
#define N 300005
using namespace std;
int a[300005],fen[4][300005],X[300005];
pair<int,int> d[300005];
void upd(int x,int idx){
    while (idx < N){
        fen[x][idx]+=1;
        idx += (idx&(-idx));
    }
}
int get(int x,int idx){
    int sum=0;
    while (idx > 0){
        sum += fen[x][idx];
        idx -= (idx&(-idx));
    }
    return sum;
}
main (){
    int n;
    cin>>n;
    for (int i=1;i<=n;i++){
        cin>>a[i];
        d[i].f = a[i],d[i].s = i;
    }
    sort(d+1,d+n+1);
    int m=1;
    for (int i=1;i<=n;i++){
        if (i > 1 && d[i - 1].f < d[i].f) m++;
        a[d[i].s] = m;
    }
    for (int i=1;i<=n;i++){
        if (a[i] > 1) X[i] = get(1,a[i] - 1);
        upd(1,a[i]);
    }
    int ans=0;
    for (int i=n;i>=1;i--){
        m=0;
        if (a[i] == 1) X[i]=0;
        else m = get(2,a[i - 1]),X[i] *= get(2,a[i] - 1);
        
        ans+=X[i];
        upd(2,a[i]);
    }
    cout<<ans;
}

Compilation message (stderr)

Mountains.cpp:27:7: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   27 | main (){
      |       ^

• 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