tpl_dynArrayHeap.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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  SOFTWARE.
*/
 
 
# ifndef TPL_DYNARRAYHEAP_H
# define TPL_DYNARRAYHEAP_H
 
# include <ah-concepts.H>
# include <algorithm>
# include <cstddef>
# include <stdexcept>
# include <utility>
 
# include <tpl_dynArray.H>
# include <ah-errors.H>
 
namespace Aleph
{
  template <typename T, class Compare>
  inline
  size_t sift_up(DynArray<T> & a, const size_t l, const size_t r, Compare & cmp) noexcept
  {
    for (size_t p, i = r; i > l; i = p)
      {
        p = u_index(i); // parent index (p = i / 2)
 
        // Prefetch grandparent for next iteration
        if (const size_t gp = u_index(p); gp >= l)
          __builtin_prefetch(&a.access(gp), 0, 1);
 
        T & ap = a.access(p);
        T & ai = a.access(i);
        if (cmp(ap, ai)) [[likely]] // heap property holds
            return i;
 
        std::swap(ap, ai); // swap and continue at parent
      }
 
    return l;
  }
 
  template <typename T, class Compare>
  inline
  void sift_down(DynArray<T> & a, const size_t l, const size_t r, Compare & cmp) noexcept
  {
    size_t i = l;
    while (true)
      {
        size_t c = l_index(i); // left child index (c = 2 * i)
        if (c > r) [[unlikely]] // no left child
            return;
 
        // Prefetch grandchildren for next iteration
        if (const size_t gc = l_index(c); gc <= r)
          __builtin_prefetch(&a.access(gc), 0, 1);
 
        T *ac = &a.access(c);
        if (c + 1 <= r) // right child exists
          {
            T *ac1 = &a.access(c + 1);
            if (cmp(*ac1, *ac)) // pick the child with higher priority
              {
                c++;
                ac = ac1;
              }
          }
 
        T & ai = a.access(i);
        if (cmp(ai, *ac)) [[likely]] // heap property holds
            return;
 
        std::swap(*ac, ai);
        i = c;
      }
  }
 
 
  template <typename T, class Compare = Aleph::less<T>>
    requires StrictWeakOrder<Compare, T>
  class DynArrayHeap : public LocateFunctions<DynArrayHeap<T, Compare>, T>,
                       public FunctionalMethods<DynArrayHeap<T, Compare>, T>,
                       public GenericKeys<DynArrayHeap<T, Compare>, T>,
                       public EqualToMethod<DynArrayHeap<T, Compare>>,
                       public StlAlephIterator<DynArrayHeap<T, Compare>>
  {
    DynArray<T> array;
    size_t num_items = 0;
 
    Compare cmp;
 
    static size_t r_index(const size_t & i) noexcept
    {
      return (i << 1) + 1; // right child index
    }
 
  public:
    using Item_Type = T;
 
    DynArrayHeap(Compare cmp_fct = Compare()) : cmp(cmp_fct)
    {
      // empty
    }
 
    Special_Ctors(DynArrayHeap, T);
 
    Args_Ctor(DynArrayHeap, T);
 
    T &top()
    {
      ah_underflow_error_if(num_items == 0) << "Heap is empty";
 
      return array.access(1);
    }
 
    const T &top() const
    {
      ah_underflow_error_if(num_items == 0) << "Heap is empty";
 
      return array.access(1);
    }
 
    T &insert(const T & key)
    {
      array.touch(++num_items) = key; // place new element
      const size_t pos = sift_up(array, 1, num_items, cmp);
      return array.access(pos);
    }
 
    T &insert(T && key)
    {
      array.touch(++num_items) = std::move(key); // place new element
      const size_t pos = sift_up(array, 1, num_items, cmp);
      return array.access(pos);
    }
 
    void reserve(size_t n)
    {
      ah_out_of_range_error_if(num_items > n) << "DynArrayHeap::reserve: n smaller than size";
      array.reserve(n);
    }
 
    T &insert_direct(const T & key)
    {
      array(++num_items) = key; // place new element
      const size_t pos = sift_up(array, 1, num_items, cmp);
      return array.access(pos);
    }
 
    T &insert_direct(T && key)
    {
      array(++num_items) = std::move(key); // place new element
      const size_t pos = sift_up(array, 1, num_items, cmp);
      return array.access(pos);
    }
 
    T &put(const T & key) { return insert(key); }
 
    T &put(T && key) { return insert(std::move(key)); }
 
    T &append(const T & key) { return insert(key); }
 
    T &append(T && key) { return insert(std::move(key)); }
 
    T getMin()
    {
      ah_underflow_error_if(num_items == 0) << "Heap is empty";
 
      T & a1 = array(1);
      T ret_val = std::move(a1);
      if (num_items > 1)
        {
          a1 = std::move(array(num_items));
          --num_items;
          sift_down(array, 1, num_items, cmp);
        }
      else
        --num_items;
 
      array.cut(num_items + 1);
 
      return ret_val;
    }
 
    T get()
    {
      return getMin();
    }
 
    T getMax()
    {
      return getMin();
    }
 
    [[nodiscard]] constexpr size_t size() const noexcept { return num_items; }
 
    [[nodiscard]] constexpr bool is_empty() const noexcept { return num_items == 0; }
 
    struct Iterator : DynArray<T>::Iterator
    {
      using Base = typename DynArray<T>::Iterator;
 
      Iterator(const DynArrayHeap & h) noexcept : Base(h.array)
      {
        if (h.num_items != 0)
          this->next_ne();
      }
 
      Iterator() = default;
 
      [[nodiscard]] bool has_curr() const noexcept
      {
        return this->curr_idx != 0 and this->curr_idx != this->array_ptr->size();
      }
 
      [[nodiscard]] long get_pos() const noexcept { return this->Base::get_pos() - 1; }
    };
 
    template <class Operation>
    bool traverse(Operation & operation)
    {
      for (Iterator it(*this); it.has_curr(); it.next_ne())
        if (not operation(it.get_curr()))
          return false;
      return true;
    }
 
    template <class Operation>
    bool traverse(Operation & operation) const
    {
      return const_cast<DynArrayHeap &>(*this).traverse<Operation>(operation);
    }
 
    template <class Operation>
    bool traverse(Operation && operation = Operation()) const
    {
      return traverse<Operation>(operation);
    }
 
    template <class Operation>
    bool traverse(Operation && operation = Operation())
    {
      return traverse<Operation>(operation);
    }
  };
} // end namespace Aleph
 
# endif // TPL_DYNARRAYHEAP_H