What is the right approach when using STL container for median calculation?

Question

Let\'s say I need to retrieve the median from a sequence of 1000000 random numeric values.

If using anything but std::list, I have no (

Answer 1

Armadillo has an implementation that looks like the one in the answer https://stackoverflow.com/a/34077478 by https://stackoverflow.com/users/2608582/matthew-fioravante

It uses one call to nth_element and one call to max_element and it is here: https://gitlab.com/conradsnicta/armadillo-code/-/blob/9.900.x/include/armadillo_bits/op_median_meat.hpp#L380

//! find the median value of a std::vector (contents is modified)
template
inline 
eT
op_median::direct_median(std::vector& X)
  {
  arma_extra_debug_sigprint();
  
  const uword n_elem = uword(X.size());
  const uword half   = n_elem/2;
  
  typename std::vector::iterator first    = X.begin();
  typename std::vector::iterator nth      = first + half;
  typename std::vector::iterator pastlast = X.end();
  
  std::nth_element(first, nth, pastlast);
  
  if((n_elem % 2) == 0)  // even number of elements
    {
    typename std::vector::iterator start   = X.begin();
    typename std::vector::iterator pastend = start + half;
    
    const eT val1 = (*nth);
    const eT val2 = (*(std::max_element(start, pastend)));
    
    return op_mean::robust_mean(val1, val2);
    }
  else  // odd number of elements
    {
    return (*nth);
    }
  }