quick sort - sorting algorithm - libreria per MetaTrader 5

//+------------------------------------------------------------------+
//|                                                    QuickSort.mq5 |
//|                                    2019-2020, dimitri pecheritsa |
//|                                                 792112@gmail.com |
//+------------------------------------------------------------------+
//
//   quick sort - sorting algorithm
//
//   quick sort is a highly efficient sorting algorithm and is based
//on partitioning of array of data into smaller arrays
//   a large array is partitioned into two arrays one of which holds
//values smaller than the specified value say pivot, based on which
//the partition is made and another array holds values greater than
//the pivot value
//   quick sort partitions an array and then calls itself recursively
//twice to sort the two resulting subarrays
//   this algorithm is quite efficient for large-sized data sets as
//its average and worst-case complexity are O(nlogn) and theta(n^2),
//respectively
//
//   quick sort pivot algorithm
//
//   step 1: choose the highest index value has pivot
//   step 2: take two variables to point left and right of the values
//excluding pivot
//   step 3: left points to the low index
//   step 4: right points to the high
//   step 5: while value at left is less than pivot move right
//   step 6: while value at right is greater than pivot move left
//   step 7: if both step 5 and step 6 does not match swap left and
//right
//   step 8: if left ≥ right, the point where they met is new pivot
//
//   quick sort algorithm
//
//   using pivot algorithm recursively, we end up with smaller
//possible partitions
//   each partition is then processed for quick sort
//   step 1: make the right-most index value pivot
//   step 2: partition the array using pivot value
//   step 3: quicksort left partition recursively
//   step 4: quicksort right partition recursively
//
//+------------------------------------------------------------------+
//| quick sort example - sort positions by open price in accending   |
//| or descending order                                              |
//+------------------------------------------------------------------+
#include <Mqh\Algorithms\QuickSort\QuickSort.mqh>
#include <Mqh\Algorithms\QuickSort\Functions.mqh>
void OnStart()
  {
//---load tickets from terminal - the items to be sorted 
   string symbol=_Symbol;
   ulong tickets[];
   PositionsLoad(tickets,symbol);
//---create keys for sorting - open prices of the positions
   double keys[];
   PositionsKeysPriceOpen(tickets,keys);
//---sort positions by open price
   CQuickSort<double,ulong> sorter;
   bool accending_order=true; //false for descending
   sorter.Sort(keys,tickets,accending_order);
//---print positions
   int digits=(int)SymbolInfoInteger(symbol,SYMBOL_DIGITS);
   PositionsPrint(tickets,digits);
  }
//
//   example output
//
//    EURUSD | 195762889 |  1.16667
//    EURUSD | 195806889 |  1.16939
//    EURUSD | 195998318 |  1.17384
//    EURUSD | 197300364 |  1.17602
//    EURUSD | 197454338 |  1.17680
//    EURUSD | 197488771 |  1.17859
//    EURUSD | 196985503 |  1.17924
//    EURUSD | 196058650 |  1.17935
//    EURUSD | 197513038 |  1.18068
//    EURUSD | 196921898 |  1.18179
//    EURUSD | 196317657 |  1.18295
//    EURUSD | 198719928 |  1.18325
//    EURUSD | 198678762 |  1.18342
//    EURUSD | 198673400 |  1.18387
//    EURUSD | 197932787 |  1.18482
//   ...
//
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