Submission #952165

#	Time	Username	Problem	Language	Result	Execution time	Memory
952165		Bzslayed	Mountains (NOI20_mountains)	C++17	100 / 100	517 ms	50768 KiB

Mountains

#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

#define ll long long
#define pll pair<ll, ll>
#define pii pair<int, int>
#define pff pair<float, float>
#define coutpair(p) cout << p.first << " " << p.second << "\n"

typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
typedef tree<ll, null_type, less_equal<ll>, rb_tree_tag, tree_order_statistics_node_update> ordered_multiset;

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int n; cin >> n;
    ll h[n];
    for (int i=0; i<n; i++) cin >> h[i];

    ordered_multiset lcnt, rcnt; //to check for bottom values
    ll left[n], right[n]; //for a fixed point i, how many numbers are 
                            //smaller than it on each side
    left[0] = 0, right[n-1] = 0;
    ll ans = 0;

    lcnt.insert(h[0]);
    for (int i=1; i<n; i++){
        left[i] = lcnt.order_of_key(h[i]);
        lcnt.insert(h[i]);
    }

    rcnt.insert(h[n-1]);
    for (int i=n-2; i>=0; i--){
        right[i] = rcnt.order_of_key(h[i]);
        ans += left[i]*right[i];
        rcnt.insert(h[i]);
    }

    cout << ans;    

    return 0;
}

• 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