Submission #294682

#	Time	Username	Problem	Language	Result	Execution time	Memory
294682		crossing0ver	Mountains (NOI20_mountains)	C++17	100 / 100	1162 ms	32084 KiB

Mountains

#include<bits/stdc++.h>
#define ll long long
#define pii pair<ll,int>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define oset tree<pii,null_type,less<pii>,rb_tree_tag,tree_order_statistics_node_update>
ll a[300005],L[300005],R[300005];
main() {
    oset s;
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    for (int i =1 ; i <= n; i++) {
        L[i] = s.order_of_key({a[i],0});
        s.insert({a[i],i});
    }
    s.clear();
    ll ans = 0;
    for (int  i = n; i > 0; i--) {
        R[i] = s.order_of_key({a[i],0});
        s.insert({a[i],i});
        ans += (ll)L[i]*R[i];
    }
    cout << ans;
}

Compilation message (stderr)

Mountains.cpp:10:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   10 | 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