heap_tpl.h

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#include <sstream>
#include <string>

// to ease IDE parser
#include <agrum/core/heap.h>

namespace gum {

  // basic constructor. Creates an empty heap
  template < typename Val, typename Cmp, typename Alloc >
  Heap< Val, Cmp, Alloc >::Heap(Cmp compare, Size capacity) : __cmp(compare) {
    __heap.reserve(capacity);

    // for debugging purposes
    GUM_CONSTRUCTOR(Heap);
  }

  // initializer list constructor
  template < typename Val, typename Cmp, typename Alloc >
  Heap< Val, Cmp, Alloc >::Heap(std::initializer_list< Val > list) {
    __heap.reserve(list.size());
    for (const auto& elt : list) {
      insert(elt);
    }

    // for debugging purposes
    GUM_CONSTRUCTOR(Heap);
  }

  // copy constructor
  template < typename Val, typename Cmp, typename Alloc >
  Heap< Val, Cmp, Alloc >::Heap(const Heap< Val, Cmp, Alloc >& from) :
      __heap(from.__heap), __nb_elements(from.__nb_elements), __cmp(from.__cmp) {
    // for debugging purposes
    GUM_CONS_CPY(Heap);
  }

  // generalized copy constructor
  template < typename Val, typename Cmp, typename Alloc >
  template < typename OtherAlloc >
  Heap< Val, Cmp, Alloc >::Heap(const Heap< Val, Cmp, OtherAlloc >& from) :
      __nb_elements(from.__nb_elements), __cmp(from.__cmp) {
    __heap.reserve(__nb_elements);

    // copy the elements of from.__heap
    for (unsigned i = 0; i < __nb_elements; ++i)
      __heap.push_back(from.__heap[i]);

    // for debugging purposes
    GUM_CONS_CPY(Heap);
  }

  // move constructor
  template < typename Val, typename Cmp, typename Alloc >
  Heap< Val, Cmp, Alloc >::Heap(Heap< Val, Cmp, Alloc >&& from) noexcept :
      __heap(std::move(from.__heap)), __nb_elements(std::move(from.__nb_elements)),
      __cmp(std::move(from.__cmp)) {
    // for debugging purposes
    GUM_CONS_MOV(Heap);
  }

  // destructor
  template < typename Val, typename Cmp, typename Alloc >
  Heap< Val, Cmp, Alloc >::~Heap() {
    // for debugging purposes
    GUM_DESTRUCTOR(Heap);
  }

  // copy operator
  template < typename Val, typename Cmp, typename Alloc >
  Heap< Val, Cmp, Alloc >& Heap< Val, Cmp, Alloc >::
                           operator=(const Heap< Val, Cmp, Alloc >& from) {
    // avoid self assignment
    if (this != &from) {
      try {
        __heap = from.__heap;
      } catch (...) {
        __heap.clear();
        __nb_elements = 0;

        throw;
      }

      // set the comparison function
      __cmp = from.__cmp;
      __nb_elements = from.__nb_elements;

      // for debugging purposes
      GUM_OP_CPY(Heap);
    }

    return *this;
  }

  // generalized copy operator
  template < typename Val, typename Cmp, typename Alloc >
  template < typename OtherAlloc >
  Heap< Val, Cmp, Alloc >& Heap< Val, Cmp, Alloc >::
                           operator=(const Heap< Val, Cmp, OtherAlloc >& from) {
    // avoid self assignment
    if (this != &from) {
      try {
        __heap.clear();

        if (__heap.capacity() < from.__nb_elements)
          __heap.reserve(from.__nb_elements);

        for (unsigned int i = 0; i < from.__nb_elements; ++i) {
          __heap.push_back(from.__heap[i]);
        }
      } catch (...) {
        __heap.clear();
        __nb_elements = 0;
        throw;
      }

      __cmp = from.__cmp;
      __nb_elements = from.__nb_elements;

      // for debugging purposes
      GUM_OP_CPY(Heap);
    }

    return *this;
  }

  // move operator
  template < typename Val, typename Cmp, typename Alloc >
  Heap< Val, Cmp, Alloc >& Heap< Val, Cmp, Alloc >::
                           operator=(Heap< Val, Cmp, Alloc >&& from) noexcept {
    // avoid self assignment
    if (this != &from) {
      __heap = std::move(from.__heap);
      __nb_elements = std::move(from.__nb_elements);
      __cmp = std::move(from.__cmp);
    }

    return *this;
  }

  // returns the element at the top of the heap
  template < typename Val, typename Cmp, typename Alloc >
  INLINE const Val& Heap< Val, Cmp, Alloc >::top() const {
    if (!__nb_elements) { GUM_ERROR(NotFound, "empty heap"); }

    return __heap[0];
  }

  // returns the number of elements in the heap
  template < typename Val, typename Cmp, typename Alloc >
  INLINE Size Heap< Val, Cmp, Alloc >::size() const noexcept {
    return __nb_elements;
  }

  // return the size of the array storing the heap
  template < typename Val, typename Cmp, typename Alloc >
  INLINE Size Heap< Val, Cmp, Alloc >::capacity() const noexcept {
    return Size(__heap.size());
  }

  // changes the size of the array storing the heap
  template < typename Val, typename Cmp, typename Alloc >
  INLINE void Heap< Val, Cmp, Alloc >::resize(Size new_size) {
    if (new_size > __nb_elements) __heap.reserve(new_size);
  }

  // removes the element at position 'index' from the heap
  template < typename Val, typename Cmp, typename Alloc >
  void Heap< Val, Cmp, Alloc >::eraseByPos(Size index) {
    if (index >= __nb_elements) return;

    // remove the element and put the last element in its place
    Val last = std::move(__heap[__nb_elements - 1]);
    __heap.pop_back();
    --__nb_elements;

    if (!__nb_elements || (index == __nb_elements)) return;

    // restore the heap property
    Size i = index;

    for (Size j = (index << 1) + 1; j < __nb_elements; i = j, j = (j << 1) + 1) {
      // let j be the max child
      if ((j + 1 < __nb_elements) && __cmp(__heap[j + 1], __heap[j])) ++j;

      // if "last" is smaller than __heap[j], "last" must be stored at index i
      if (__cmp(last, __heap[j])) break;

      __heap[i] = std::move(__heap[j]);
    }

    __heap[i] = std::move(last);
  }

  // removes a given element from the heap (but does not return it)
  template < typename Val, typename Cmp, typename Alloc >
  INLINE void Heap< Val, Cmp, Alloc >::erase(const Val& val) {
    // find val in the heap
    for (Size i = 0; i < __nb_elements; ++i)
      if (__heap[i] == val) {
        eraseByPos(i);
        break;
      }
  }

  // removes the top of the heap (but does not return it)
  template < typename Val, typename Cmp, typename Alloc >
  INLINE void Heap< Val, Cmp, Alloc >::eraseTop() {
    // if the heap is empty, do nothing
    if (!__nb_elements) return;
    eraseByPos(0);
  }

  // removes the top element from the heap and return it
  template < typename Val, typename Cmp, typename Alloc >
  INLINE Val Heap< Val, Cmp, Alloc >::pop() {
    if (!__nb_elements) { GUM_ERROR(NotFound, "empty heap"); }

    Val v = __heap[0];
    eraseByPos(0);
    return v;
  }

  // after inserting an element at the end of the heap, restore heap property
  template < typename Val, typename Cmp, typename Alloc >
  Size Heap< Val, Cmp, Alloc >::__restoreHeap() {
    // get the element at the end of the heap
    Size i = __nb_elements - 1;
    Val  v = std::move(__heap[i]);

    // restore the heap property
    for (Size j = (i - 1) >> 1; i && __cmp(v, __heap[j]); i = j, j = (j - 1) >> 1)
      __heap[i] = std::move(__heap[j]);

    __heap[i] = std::move(v);

    return i;
  }

  // inserts a new (a copy) element in the heap
  template < typename Val, typename Cmp, typename Alloc >
  INLINE Size Heap< Val, Cmp, Alloc >::insert(const Val& val) {
    // create a new element at the end of the heap
    __heap.push_back(val);
    ++__nb_elements;
    return __restoreHeap();
  }

  // inserts a new (a copy) element in the heap
  template < typename Val, typename Cmp, typename Alloc >
  Size Heap< Val, Cmp, Alloc >::insert(Val&& val) {
    // create a new element at the end of the heap
    __heap.push_back(std::move(val));
    ++__nb_elements;
    return __restoreHeap();
  }

  // emplace a new element in the heap
  template < typename Val, typename Cmp, typename Alloc >
  template < typename... Args >
  Size Heap< Val, Cmp, Alloc >::emplace(Args&&... args) {
    // create a new element at the end of the heap
    __heap.emplace_back(std::forward< Args >(args)...);
    ++__nb_elements;
    return __restoreHeap();
  }

  // indicates whether the heap is empty
  template < typename Val, typename Cmp, typename Alloc >
  INLINE bool Heap< Val, Cmp, Alloc >::empty() const noexcept {
    return (__nb_elements == 0);
  }

  // indicates whether the heap contains a given value
  template < typename Val, typename Cmp, typename Alloc >
  INLINE bool Heap< Val, Cmp, Alloc >::contains(const Val& val) const {
    for (Size i = 0; i < __nb_elements; ++i)
      if (__heap[i] == val) return true;

    return false;
  }

  // returns the element at index elt from the heap
  template < typename Val, typename Cmp, typename Alloc >
  INLINE const Val& Heap< Val, Cmp, Alloc >::operator[](Size index) const {
    // check if the element exists
    if (index >= __nb_elements) {
      GUM_ERROR(NotFound, "not enough elements in the heap");
    }

    return __heap[index];
  }

  // displays the content of the heap
  template < typename Val, typename Cmp, typename Alloc >
  std::string Heap< Val, Cmp, Alloc >::toString() const {
    bool              deja = false;
    std::stringstream stream;
    stream << "[";

    for (Size i = 0; i != __nb_elements; ++i, deja = true) {
      if (deja) stream << " , ";

      stream << __heap[i];
    }

    stream << "]";

    return stream.str();
  }

  // A \c << operator for Heap
  template < typename Val, typename Cmp, typename Alloc >
  INLINE std::ostream& operator<<(std::ostream&                  stream,
                                  const Heap< Val, Cmp, Alloc >& heap) {
    stream << heap.toString();
    return stream;
  }

} /* namespace gum */