Submission #1135433

#	Time	Username	Problem	Language	Result	Execution time	Memory
1135433		monostack	Mountains (NOI20_mountains)	C++20	100 / 100	535 ms	47408 KiB

Mountains

#include<bits/stdc++.h>
using namespace std;
#include<ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;

template<class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

#define int long long
#define ff first
#define ss second
#define all(x) x.begin(), x.end()

void init(){
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    if(fopen("input.txt","r")){
        freopen("input.txt","r",stdin);
        freopen("output.txt","w",stdout);
    }
}

int32_t main(){
    init();
    int n, ans = 0; cin>>n;
    vector<pair<int,int>> a(n);
    for(int i=0; i < n; i++) cin>>a[i].ff, a[i].ss=i;
    ordered_set<pair<int,int>> _l, _g;
    vector<int> less_(n,0), greater_(n,0);
    for(int i = 0; i < n; i++){
        less_[i] = _l.order_of_key({a[i].ff,-1});
        greater_[n-i-1] = _g.order_of_key({a[n-i-1].ff,-1});
        _l.insert(a[i]);
        _g.insert(a[n-i-1]);
    }
    for(int i = 0; i < n; i++) ans += less_[i]*greater_[i];
    cout<<ans;
}

Compilation message (stderr)

Mountains.cpp: In function 'void init()':
Mountains.cpp:18:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   18 |         freopen("input.txt","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
Mountains.cpp:19:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |         freopen("output.txt","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• 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