Submission #339794

#	Time	Username	Problem	Language	Result	Execution time	Memory
339794		mihai145	Mountains (NOI20_mountains)	C++14	24 / 100	691 ms	11372 KiB

Mountains

#include <iostream>
#include <set>
#include <map>

using namespace std;

const int NMAX = 3e5;

int N, v[NMAX + 5];
set <int> xs;

int k;
map <int, 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];
        xs.insert(v[i]);
    }

    while(!xs.empty()) {
        int val = *xs.begin();
        xs.erase(xs.begin());
        norm[val] = ++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 = 0;
    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: 0 / 36
• Subtask 5: 0 / 28
• Subtask 6: 9 / 9
• Subtask 7: 0 / 12