std::ranges::pop_heap - cppreference.com

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Defined in header `<algorithm>`
Call signature
`template< std::random_access_iterator I, std::sentinel_for<I> S, class Comp = ranges::less, class Proj = std::identity > requires std::sortable<I, Comp, Proj> constexpr I pop_heap( I first, S last, Comp comp = {}, Proj proj = {} );`	(1)	(since C++20)
`template< ranges::random_access_range R, class Comp = ranges::less, class Proj = std::identity > requires std::sortable<ranges::iterator_t<R>, Comp, Proj> constexpr ranges::borrowed_iterator_t<R> pop_heap( R&& r, Comp comp = {}, Proj proj = {} );`	(2)	(since C++20)

Swaps the first element and the last element of the specified heap with respect to comp and proj and makes the subrange excluding the first position into a heap with respect to comp and proj. This has the effect of removing the first element from the specified heap.

1) The specified heap is [first, last).

2) The specified heap is r.

The function-like entities described on this page are algorithm function objects (informally known as niebloids), that is:

Explicit template argument lists cannot be specified when calling any of them.
None of them are visible to argument-dependent lookup.
When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup is inhibited.

Parameters

first, last	-	the iterator-sentinel pair defining the range of elements to modify
r	-	the `range` of elements to modify
comp	-	comparator to apply to the projected elements
proj	-	projection to apply to the elements

Return value

1) last

2) ranges::end(r)

Complexity

At most 2log(N) applications of comp and 4log(N) applications of proj, where N is:

1) ranges::distance(first, last)

2) ranges::distance(r)

Example

#include <algorithm>
#include <array>
#include <iostream>
#include <iterator>
#include <string_view>

template<class I = int*>
void print(std::string_view rem, I first = {}, I last = {},
           std::string_view term = "\n")
{
    for (std::cout << rem; first != last; ++first)
        std::cout << *first << ' ';
    std::cout << term;
}

int main()
{
    std::array v{3, 1, 4, 1, 5, 9, 2, 6, 5, 3};
    print("initially, v: ", v.cbegin(), v.cend());
    
    std::ranges::make_heap(v);
    print("make_heap, v: ", v.cbegin(), v.cend());
    
    print("convert heap into sorted array:");
    for (auto n {std::ssize(v)}; n >= 0; --n)
    {
        std::ranges::pop_heap(v.begin(), v.begin() + n);
        print("[ ", v.cbegin(), v.cbegin() + n, "]  ");
        print("[ ", v.cbegin() + n, v.cend(), "]\n");
    }
}

Output:

initially, v: 3 1 4 1 5 9 2 6 5 3
make_heap, v: 9 6 4 5 5 3 2 1 1 3
convert heap into sorted array:
[ 6 5 4 3 5 3 2 1 1 9 ]  [ ]
[ 5 5 4 3 1 3 2 1 6 ]  [ 9 ]
[ 5 3 4 1 1 3 2 5 ]  [ 6 9 ]
[ 4 3 3 1 1 2 5 ]  [ 5 6 9 ]
[ 3 2 3 1 1 4 ]  [ 5 5 6 9 ]
[ 3 2 1 1 3 ]  [ 4 5 5 6 9 ]
[ 2 1 1 3 ]  [ 3 4 5 5 6 9 ]
[ 1 1 2 ]  [ 3 3 4 5 5 6 9 ]
[ 1 1 ]  [ 2 3 3 4 5 5 6 9 ]
[ 1 ]  [ 1 2 3 3 4 5 5 6 9 ]
[ ]  [ 1 1 2 3 3 4 5 5 6 9 ]

ranges::push_heap (C++20)	adds an element to a max heap (algorithm function object)[edit]
ranges::is_heap (C++20)	checks if the given range is a max heap (algorithm function object)[edit]
ranges::is_heap_until (C++20)	finds the largest subrange that is a max heap (algorithm function object)[edit]
ranges::make_heap (C++20)	creates a max heap out of a range of elements (algorithm function object)[edit]
ranges::sort_heap (C++20)	turns a max heap into a range of elements sorted in ascending order (algorithm function object)[edit]
pop_heap	removes the largest element from a max heap (function template) [edit]

Parameters

Return value

Complexity

Example

See also