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std::make_heap(3)	       C++ Standard Libary	       std::make_heap(3)

NAME
     std::make_heap - std::make_heap

Synopsis
	Defined in header <algorithm>
	template<  class RandomIt >				  (1) (constexpr
     since C++20)
	void make_heap( RandomIt first, RandomIt last );
	template< class RandomIt, class Compare >
	void make_heap( RandomIt first, RandomIt last, Compare	 (2)  (constexpr
     since C++20)
	comp );

	Constructs a heap in the range [first, last).

	1) The constructed heap is with respect to
	operator<
	(until C++20)
	std::less{}
	(since C++20).
	2) The constructed heap is with respect to comp.

	If  any  of the following conditions is satisfied, the behavior is unde-
     fined:

	  * The type of *first is not Swappable.	   (until C++11)
	  * RandomIt is not ValueSwappable.
	  * The type of *first is not MoveConstructible.   (since C++11)
	  * The type of *first is not MoveAssignable.

Parameters
	first, last -  the range to make the heap from
		       comparison function object (i.e. an object that satisfies
     the
		       requirements of Compare) which returns true if the  first
     argument is
		       less than the second.

		       The signature of the comparison function should be equiv-
     alent to the
		       following:

		       bool cmp(const Type1& a, const Type2& b);
	comp	    -
		       While  the  signature  does  not need to have const&, the
     function must
		       not modify the objects passed to it and must be	able  to
     accept all
		       values  of  type (possibly const) Type1 and Type2 regard-
     less of value
		       category (thus, Type1& is not allowed
		       , nor is Type1 unless for Type1 a move is equivalent to a
     copy
		       (since C++11)).
		       The types Type1 and Type2 must be such that an object  of
     type
		       RandomIt  can  be  dereferenced	and then implicitly con-
     verted to both of
		       them.

Type requirements
	-
	RandomIt must meet the requirements of LegacyRandomAccessIterator.
	-
	Compare must meet the requirements of Compare.

Complexity
	Given \(\scriptsize N\)N as std::distance(first, last):

	1) At most \(\scriptsize 3N\)3N comparisons using
	operator<
	(until C++20)
	std::less{}
	(since C++20).
	2) At most \(\scriptsize 3N\)3N applications of the comparison	function
     comp.

Example
     // Run this code

      #include <algorithm>
      #include <functional>
      #include <iostream>
      #include <string_view>
      #include <vector>

      void print(std::string_view text, const std::vector<int>& v = {})
      {
	  std::cout << text << ": ";
	  for (const auto& e : v)
	      std::cout << e << ' ';
	  std::cout << '\n';
      }

      int main()
      {
	  print("Max heap");

	  std::vector<int> v{3, 2, 4, 1, 5, 9};
	  print("initially, v", v);

	  std::make_heap(v.begin(), v.end());
	  print("after make_heap, v", v);

	  std::pop_heap(v.begin(), v.end());
	  print("after pop_heap, v", v);

	  auto top = v.back();
	  v.pop_back();
	  print("former top element", {top});
	  print("after removing the former top element, v", v);

	  print("\nMin heap");

	  std::vector<int> v1{3, 2, 4, 1, 5, 9};
	  print("initially, v1", v1);

	  std::make_heap(v1.begin(), v1.end(), std::greater<>{});
	  print("after make_heap, v1", v1);

	  std::pop_heap(v1.begin(), v1.end(), std::greater<>{});
	  print("after pop_heap, v1", v1);

	  auto top1 = v1.back();
	  v1.pop_back();
	  print("former top element", {top1});
	  print("after removing the former top element, v1", v1);
      }

Output:
      Max heap:
      initially, v: 3 2 4 1 5 9
      after make_heap, v: 9 5 4 1 2 3
      after pop_heap, v: 5 3 4 1 2 9
      former top element: 9
      after removing the former top element, v: 5 3 4 1 2

      Min heap:
      initially, v1: 3 2 4 1 5 9
      after make_heap, v1: 1 2 4 3 5 9
      after pop_heap, v1: 2 3 4 9 5 1
      former top element: 1
      after removing the former top element, v1: 2 3 4 9 5

	Defect reports

	The  following	behavior-changing  defect  reports were applied retroac-
     tively to
	previously published C++ standards.

	   DR	 Applied to		 Behavior as published		    Cor-
     rect behavior
	LWG 3032 C++98	    the elements of [first, last) was not required   re-
     quired
			    to be swappable

See also
	is_heap 	  checks if the given range is a max heap
	(C++11) 	  (function template)
	is_heap_until	  finds the largest subrange that is a max heap
	(C++11) 	  (function template)
	push_heap	  adds an element to a max heap
			  (function template)
	pop_heap	  removes the largest element from a max heap
			  (function template)
			  turns  a  max  heap into a range of elements sorted in
     ascending
	sort_heap	  order
			  (function template)
	priority_queue	  adapts a container to provide priority queue
			  (class template)
	ranges::make_heap creates a max heap out of a range of elements
	(C++20) 	  (niebloid)

http://cppreference.com 	   2024.06.10		       std::make_heap(3)
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