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

NAME
     std::is_heap - std::is_heap

Synopsis
	Defined in header <algorithm>
	template<  class  RandomIt  >				     (1)  (since
     C++11)
	bool is_heap( RandomIt first, RandomIt last );		      (constexpr
     since C++20)
	template< class ExecutionPolicy, class RandomIt >

	bool  is_heap(	ExecutionPolicy&&  policy,		     (2)  (since
     C++17)

		      RandomIt first, RandomIt last );
	template< class  RandomIt,  class  Compare  >			  (since
     C++11)
	bool  is_heap( RandomIt first, RandomIt last, Compare	  (3) (constexpr
     since C++20)
	comp );
	template< class ExecutionPolicy, class RandomIt, class
	Compare >

	bool  is_heap(	ExecutionPolicy&&  policy,		     (4)  (since
     C++17)

		      RandomIt first, RandomIt last, Compare
	comp );

	Checks whether [first, last) is a heap.

	1) The heap property to be checked is with respect to
	operator<
	(until C++20)
	std::less{}
	(since C++20).
	3) The heap property to be checked is with respect to comp.
	2,4) Same as (1,3), but executed according to policy.
	These overloads participate in overload resolution only if

	std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>    is    true.
     (until
										  C++20)
	std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>      is
     true. (since
										  C++20)

Parameters
	first, last -  the range to be checked
	policy	    -  the execution policy to use. See execution policy for de-
     tails.
		       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.

Return value
	true  if  the range is a heap with respect to the corresponding compara-
     tor, false
	otherwise.

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

	1,2) \(\scriptsize O(N)\)O(N) comparisons using
	operator<
	(until C++20)
	std::less{}
	(since C++20).
	3,4) \(\scriptsize O(N)\)O(N) applications of  the  comparison	function
     comp.

Exceptions
	The overloads with a template parameter named ExecutionPolicy report er-
     rors as
	follows:

	  *  If  execution of a function invoked as part of the algorithm throws
     an exception
	    and ExecutionPolicy is one of the standard policies,  std::terminate
     is called.
	    For  any  other  ExecutionPolicy, the behavior is implementation-de-
     fined.
	  * If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Example
     // Run this code

      #include <algorithm>
      #include <bit>
      #include <iostream>
      #include <vector>

      int main()
      {
	  std::vector<int> v{3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9};

	  std::cout << "initially, v:\n";
	  for (const auto& i : v)
	      std::cout << i << ' ';
	  std::cout << '\n';

	  if (!std::is_heap(v.begin(), v.end()))
	  {
	      std::cout << "making heap...\n";
	      std::make_heap(v.begin(), v.end());
	  }

	  std::cout << "after make_heap, v:\n";
	  for (auto t{1U}; const auto& i : v)
	      std::cout << i << (std::has_single_bit(++t) ? " | " : " ");
	  std::cout << '\n';
      }

Output:
      initially, v:
      3 1 4 1 5 9 2 6 5 3 5 8 9 7 9
      making heap...
      after make_heap, v:
      9 | 6 9 | 5 5 9 7 | 1 1 3 5 8 3 4 2 |

See also
	is_heap_until	finds the largest subrange that is a max heap
	(C++11) 	(function template)
	make_heap	creates a max heap out of a range of elements
			(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)
	sort_heap	turns a max heap into a range of elements sorted in  as-
     cending order
			(function template)
	ranges::is_heap checks if the given range is a max heap
	(C++20) 	(niebloid)

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