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std::ranges::pop_heap(3) C++ Standard Libary std::ranges::pop_heap(3) NAME std::ranges::pop_heap - std::ranges::pop_heap Synopsis 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> (1) (since C++20) constexpr I pop_heap( I first, S last, Comp comp = {}, Proj proj = {} ); template< ranges::random_access_range R, class Comp = ranges::less, class Proj = std::identity > (2) (since C++20) requires std::sortable<ranges::iterator_t<R>, Comp, Proj> constexpr ranges::borrowed_iterator_t<R> pop_heap( R&& r, Comp comp = {}, Proj proj = {} ); Swaps the value in the position first and the value in the position last - 1 and makes the subrange [first, last - 1) into a max heap. This has the effect of removing the first element from the heap defined by the range [first, last). 1) Elements are compared using the given binary comparison function comp and projection object proj. 2) Same as (1), but uses r as the range, as if using ranges::be- gin(r) as first and ranges::end(r) as last. The function-like entities described on this page are niebloids, that is: * Explicit template argument lists cannot be specified when call- ing 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 in- hibited. In practice, they may be implemented as function objects, or with special compiler extensions. Parameters first, last - the range of elements defining the valid nonempty heap to modify r - the range of elements defining the valid nonempty heap to modify pred - predicate to apply to the projected elements proj - projection to apply to the elements Return value An iterator equal to last. Complexity Given N = ranges::distance(first, last), at most \(\scriptsize 2\log{(N)}\)2log(N) comparisons and \(\scriptsize 4\log{(N)}\)4log(N) projections. Notes A max heap is a range of elements [f, l), arranged with respect to comparator comp and projection proj, that has the following properties: * With N = l - f, p = f[(i - 1) / 2], and q = f[i], for all 0 < i < N, the expression std::invoke(comp, std::invoke(proj, p), std::in- voke(proj, q)) evaluates to false. * A new element can be added using ranges::push_heap, in \(\scriptsize \mathcal{O}(\log N)\)(log N) time. * The first element can be removed using ranges::pop_heap, in \(\scriptsize \mathcal{O}(\log N)\)(log N) time. Example // Run this code #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 ] See also ranges::push_heap adds an element to a max heap (C++20) (niebloid) ranges::is_heap checks if the given range is a max heap (C++20) (niebloid) ranges::is_heap_until finds the largest subrange that is a max heap (C++20) (niebloid) ranges::make_heap creates a max heap out of a range of elements (C++20) (niebloid) ranges::sort_heap turns a max heap into a range of elements sorted in ascending (C++20) order (niebloid) pop_heap removes the largest element from a max heap (function template) http://cppreference.com 2024.06.10 std::ranges::pop_heap(3)
NAME | Synopsis | Parameters | Return value | Complexity | Notes | Example | Output: | See also
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