Submission #680222

#	Time	Username	Problem	Language	Result	Execution time	Memory
680222		raysh07	Mountains (NOI20_mountains)	C++17	100 / 100	703 ms	52880 KiB

Mountains

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define INF (int)1e18

mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());
int n;
const int maxn = 3e5 + 69;
int a[maxn];
set <int> send;
map <int, int> comp;
int seg[4*maxn];
int b[maxn];

void Update(int l, int r, int pos, int qpos, int qval){
    seg[pos]+=qval;
    if (l==r) return;
    int mid = (l+r)/2;
    if (qpos<=mid) Update(l, mid, pos*2, qpos, qval);
    else Update(mid + 1, r, pos*2 + 1, qpos, qval);
}

int Query(int l, int r, int pos, int ql, int qr){
    if (l>=ql && r<=qr) return seg[pos];
    else if (l>qr || r<ql) return 0;
    
    int mid = (l+r)/2;
    return Query(l, mid, pos*2, ql, qr) + Query(mid + 1, r, pos*2 + 1, ql, qr);
}

void compress()
{
    int p = 1;
    for (auto x: send){
        comp[x] = p++;
    }
}

void Solve() 
{
    cin>>n;
    for (int i=1; i<=n; i++){
        cin>>a[i];
        send.insert(a[i]);
    }
    compress();
    
    for (int i=1; i<=n; i++)
    a[i] = comp[a[i]];
    
    for (int i=1; i<=n; i++){
        b[i] = Query(1, n, 1, 1, a[i]-1);
        Update(1, n, 1, a[i], 1);
    }
    
    for (int i=0; i<4*maxn; i++)
    seg[i] = 0;
    
    int sum = 0;
    
    for (int i=n; i>=1; i--){
        b[i] *= Query(1, n, 1, 1, a[i]-1);
        Update(1, n, 1, a[i], 1);
        
        sum += b[i];
    }
    
    cout<<sum;
}

int32_t main() 
{
    auto begin = std::chrono::high_resolution_clock::now();
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int t = 1;
    //cin >> t;
    for(int i = 1; i <= t; i++) 
    {
        //cout << "Case #" << i << ": ";
        Solve();
    }
    auto end = std::chrono::high_resolution_clock::now();
    auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
    cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n"; 
    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