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std::sort_heap

From cppreference.com
 
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Non-modifying sequence operations    
Batch operations
(C++17)
Search operations
Modifying sequence operations
Copy operations
(C++11)
(C++11)
Swap operations
Transformation operations
Generation operations
Removing operations
Order-changing operations
(until C++17)(C++11)
(C++20)(C++20)
Sampling operations
(C++17)

Sorting and related operations
Partitioning operations
(C++11)    

Sorting operations
Binary search operations
(on partitioned ranges)
Set operations (on sorted ranges)
Merge operations (on sorted ranges)
Heap operations
Minimum/maximum operations
(C++11)
(C++17)
Lexicographical comparison operations
Permutation operations


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

Converts the heap represented by the target range [first, last) into a sorted range. The heap property is no longer maintained.

1) The target range will be sorted with respect to operator<(until C++20)std::less{}(since C++20).
If the target range does not originally represent a heap with respect to operator<(until C++20)std::less{}(since C++20), the behavior is undefined.
2) The target range will be sorted with respect to comp.
If the target range does not originally represent a heap with respect to comp, the behavior is undefined.

If any of the following conditions is satisfied, the behavior is undefined:

(until C++11)
(since C++11)

Parameters

first, last - the pair of iterators defining the target range
comp - 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 equivalent to the following:

bool cmp(const Type1& a, const Type2& b);

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 regardless 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 converted to both of them.

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

Complexity

Given N as std::distance(first, last):

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

Possible implementation

sort_heap (1)
template<class RandomIt>
void sort_heap(RandomIt first, RandomIt last)
{
    while (first != last)
        std::pop_heap(first, last--);
}
sort_heap (2)
template<class RandomIt, class Compare>
void sort_heap(RandomIt first, RandomIt last, Compare comp)
{
    while (first != last)
        std::pop_heap(first, last--, comp);
}

Example

import std;

int main()
{
    std::array v{3, 1, 4, 1, 5, 9};
    std::print("original state:  {}\n", v);

    std::make_heap(v.begin(), v.end());
    std::print("after make_heap: {}\n", v);

    std::sort_heap(v.begin(), v.end());
    std::print("after sort_heap: {}\n", v);
}

Output:

original state:  [3, 1, 4, 1, 5, 9]
after make_heap: [9, 5, 4, 1, 1, 3]
after sort_heap: [1, 1, 3, 4, 5, 9]

Defect reports

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

DR Applied to Behavior as published Correct behavior
LWG 2444 C++98 at most N⋅log(N) comparisons were allowed increased to 2N⋅log(N)

See also

turns a max heap into a sorted range of elements
(algorithm function object)[edit]
(C++11)
checks if the given range is a max heap
(function template & algorithm function object)[edit]
finds the largest subrange that is a max heap
(function template & algorithm function object)[edit]
creates a max heap out of a range of elements
(function template & algorithm function object)[edit]
removes the largest element from a max heap
(function template & algorithm function object)[edit]
adds an element to a max heap
(function template & algorithm function object)[edit]