Language: C++

#include<bits/stdc++.h>
using namespace std;

#define se second
#define fi first
#define mk(a,b) make_pair(a,b)

typedef long long ll;
typedef pair<ll,ll> pii;

ll N;
ll A[100010];

class BIT
{
public:
    vector<ll> bit;
    int M;

    BIT(int M):
        bit(vector<int>(M + 1, 0)), M(M + 1) {}

    int sum(int i)
    {
        if(!i)return 0;
        return bit[i] + sum(i - (i & -i));
    }

    void add(int i, int x)
    {
        if(i > M)return;
        bit[i] += x;
        add(i + (i & -i), x);
    }
};

bool judge(int mid)
{
    ll mem[100010] = {0};
    for(int i = 0; i < N; i++)
    {
        if(A[i] <= mid)mem[i] = 1;
        else mem[i] = -1;
    }

    vector<pii> v;
    ll tmp = 0;
    for(int i = 0; i < N; i++)
    {
        tmp += mem[i];

        v.push_back(mk(tmp, -i - 1));
    }
    v.push_back(mk(0,0));

    sort(v.begin(), v.end());

    BIT bit(N + 10);
    ll sum = 0;
    for(int i = 0; i < v.size(); i++)
    {
        sum += bit.sum(-v[i].se + 1);
        bit.add(-v[i].se + 1, 1);
    }

    if(N * (N + 1) / 2 < sum * 2)return true;
    return false;
}

int main()
{
    cin >> N;
    for(int i = 0; i < N; i++)cin >> A[i];

    int l = 0, r = 1000000001;
    for(int i = 0; i < 100; i++)
    {
        int mid = (l + r) / 2;
        if(judge(mid))r = mid;
        else l = mid;
    }
    cout << r << endl;
    return 0;
}


Compiler output:
a.cc: In constructor 'BIT::BIT(int)':
a.cc:21:9: error: no matching function for call to 'std::vector<long long int>::vector(std::vector<int>)'
   21 |         bit(vector<int>(M + 1, 0)), M(M + 1) {}
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_vector.h:707:9: note: candidate: 'template<class _InputIterator, class> std::vector<_Tp, _Alloc>::vector(_InputIterator, _InputIterator, const allocator_type&) [with <template-parameter-2-2> = _InputIterator; _Tp = long long int; _Alloc = std::allocator<long long int>]'
  707 |         vector(_InputIterator __first, _InputIterator __last,
      |         ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:707:9: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:678:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::initializer_list<_Tp>, const allocator_type&) [with _Tp = long long int; _Alloc = std::allocator<long long int>; allocator_type = std::allocator<long long int>]'
  678 |       vector(initializer_list<value_type> __l,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:678:43: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::initializer_list<long long int>'
  678 |       vector(initializer_list<value_type> __l,
      |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:659:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, std::__type_identity_t<_Alloc>&) [with _Tp = long long int; _Alloc = std::allocator<long long int>; std::__type_identity_t<_Alloc> = std::allocator<long long int>]'
  659 |       vector(vector&& __rv, const __type_identity_t<allocator_type>& __m)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:659:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:640:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, const allocator_type&, std::false_type) [with _Tp = long long int; _Alloc = std::allocator<long long int>; allocator_type = std::allocator<long long int>; std::false_type = std::false_type]'
  640 |       vector(vector&& __rv, const allocator_type& __m, false_type)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:640:7: note:   candidate expects 3 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:635:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&, const allocator_type&, std::true_type) [with _Tp = long long int; _Alloc = std::allocator<long long int>; allocator_type = std::allocator<long long int>; std::true_type = std::true_type]'
  635 |       vector(vector&& __rv, const allocator_type& __m, true_type) noexcept
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:635:7: note:   candidate expects 3 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:624:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&, std::__type_identity_t<_Alloc>&) [with _Tp = long long int; _Alloc = std::allocator<long long int>; std::__type_identity_t<_Alloc> = std::allocator<long long int>]'
  624 |       vector(const vector& __x, const __type_identity_t<allocator_type>& __a)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:624:7: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:620:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(std::vector<_Tp, _Alloc>&&) [with _Tp = long long int; _Alloc = std::allocator<long long int>]'
  620 |       vector(vector&&) noexcept = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:620:14: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::vector<long long int>&&'
  620 |       vector(vector&&) noexcept = default;
      |              ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:601:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp = long long int; _Alloc = std::allocator<long long int>]'
  601 |       vector(const vector& __x)
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:601:28: note:   no known conversion for argument 1 from 'std::vector<int>' to 'const std::vector<long long int>&'
  601 |       vector(const vector& __x)
      |              ~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:569:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(size_type, const value_type&, const allocator_type&) [with _Tp = long long int; _Alloc = std::allocator<long long int>; size_type = long unsigned int; value_type = long long int; allocator_type = std::allocator<long long int>]'
  569 |       vector(size_type __n, const value_type& __value,
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:569:7: note:   candidate expects 3 arguments, 1 provided
/usr/include/c++/14/bits/stl_vector.h:556:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(size_type, const allocator_type&) [with _Tp = long long int; _Alloc = std::allocator<long long int>; size_type = long unsigned int; allocator_type = std::allocator<long long int>]'
  556 |       vector(size_type __n, const allocator_type& __a = allocator_type())
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:556:24: note:   no known conversion for argument 1 from 'std::vector<int>' to 'std::vector<long long int>::size_type' {aka 'long unsigned int'}
  556 |       vector(size_type __n, const allocator_type& __a = allocator_type())
      |              ~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:542:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector(const allocator_type&) [with _Tp = long long int; _Alloc = std::allocator<long long int>; allocator_type = std::allocator<long long int>]'
  542 |       vector(const allocator_type& __a) _GLIBCXX_NOEXCEPT
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:542:36: note:   no known conversion for argument 1 from 'std::vector<int>' to 'const std::vector<long long int>::allocator_type&' {aka 'const std::allocator<long long int>&'}
  542 |       vector(const allocator_type& __a) _GLIBCXX_NOEXCEPT
      |              ~~~~~~~~~~~~~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:531:7: note: candidate: 'std::vector<_Tp, _Alloc>::vector() [with _Tp = long long int; _Alloc = std::allocator<long long int>]'
  531 |       vector() = default;
      |       ^~~~~~
/usr/include/c++/14/bits/stl_vector.h:531:7: note:   candidate expects 0 arguments, 1 provided