Submission #339796

#	Time	Username	Problem	Language	Result	Execution time	Memory
339796		mihai145	Mountains (NOI20_mountains)	C++14	100 / 100	649 ms	27660 KiB

Mountains

#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;

const int NMAX = 3e5;

int N;
long long v[NMAX + 5], vv[NMAX + 5];

int k;
unordered_map <long long, int> norm;

int st[NMAX + 5], dr[NMAX + 5];

struct AIB
{
    int n, v[NMAX + 5];

    void Reset(int _n)
    {
        n = _n;
        for(int i = 0; i <= n; i++)
            v[i] = 0;
    }

    int Lsb(int x)
    {
        return x & (-x);
    }

    void Update(int pos, int val)
    {
        for(int i = pos; i <= n; i += Lsb(i))
            v[i] += val;
    }

    int Query(int pos)
    {
        int ans = 0;

        for(int i = pos; i > 0; i -= Lsb(i))
            ans += v[i];

        return ans;
    }
};

AIB aib;

int main()
{
    cin >> N;

    for(int i = 1; i <= N; i++)
    {
        cin >> v[i];
        vv[i] = v[i];
    }

    sort(vv + 1, vv + N + 1);

    for(int i = 2; i <= N; i++)
        if(vv[i] != vv[i - 1])
            norm[vv[i - 1]] = ++k;

    norm[vv[N]] = ++k;

    aib.Reset(N);
    for(int i = 1; i <= N; i++)
    {
        st[i] = aib.Query(norm[v[i]] - 1);
        aib.Update(norm[v[i]], 1);
    }

    aib.Reset(N);
    for(int i = N; i >= 1; i--)
    {
        dr[i] = aib.Query(norm[v[i]] - 1);
        aib.Update(norm[v[i]], 1);
    }

    long long sol = 0LL;
    for(int i = 1; i <= N; i++)
        sol += 1LL * st[i] * dr[i];

    cout << sol << '\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