std::ranges::is_heap - cppreference.com (original) (raw)

Checks whether the specified range represents a heap with respect to comp and proj.

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

2. The specified range 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.

Contents

• 1 Parameters
• 2 Return value
• 3 Complexity
• 4 Possible implementation
• 5 Example
• 6 See also

[edit] Parameters

[edit] Return value

[edit] Complexity

\(\scriptsize O(N) \)O(N) applications of comp and proj, where \(\scriptsize N \)N is:

[edit] Possible implementation

struct is_heap_fn { template<std::random_access_iterator I, std::sentinel_for S, class Proj = std::identity, std::indirect_strict_weak_order <std::projected<I, Proj>> Comp = ranges::less> constexpr bool operator()(I first, S last, Comp comp = {}, Proj proj = {}) const { return (last == ranges::is_heap_until(first, last, std::move(comp), std::move(proj))); }   template<ranges::random_access_range R, class Proj = std::identity, std::indirect_strict_weak_order <std::projected<ranges::iterator_t, Proj>> Comp = ranges::less> constexpr bool operator()(R&& r, Comp comp = {}, Proj proj = {}) const { return (*this)(ranges::begin(r), ranges::end(r), std::move(comp), std::move(proj)); } };   inline constexpr is_heap_fn is_heap{};

[edit] Example

#include #include #include #include #include   void out(const auto& what, int n = 1) { while (n-- > 0) std::cout << what; }   void draw_heap(const auto& v) { auto bails = [](int n, int w) { auto b = [](int w) { out("┌"), out("─", w), out("┴"), out("─", w), out("┐"); }; n /= 2; if (!n) return; for (out(' ', w); n-- > 0;) b(w), out(' ', w + w + 1); out('\n'); };   auto data = [](int n, int w, auto& first, auto last) { for (out(' ', w); n-- > 0 && first != last; ++first) out(*first), out(' ', w + w + 1); out('\n'); };   auto tier = [&](int t, int m, auto& first, auto last) { const int n{1 << t}; const int w{(1 << (m - t - 1)) - 1}; bails(n, w), data(n, w, first, last); };   const int m{static_cast(std::ceil(std::log2(1 + v.size())))}; auto first{v.cbegin()}; for (int i{}; i != m; ++i) tier(i, m, first, v.cend()); }   int main() { std::vector v{3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9, 3, 2, 3, 8};   out("initially, v:\n"); for (auto i : v) std::cout << i << ' '; out('\n');   if (!std::ranges::is_heap(v)) { out("making heap...\n"); std::ranges::make_heap(v); }   out("after make_heap, v:\n"); for (auto t{1U}; auto i : v) std::cout << i << (std::has_single_bit(++t) ? " │ " : " ");   out("\n" "corresponding binary tree is:\n"); draw_heap(v); }

Output:

initially, v: 3 1 4 1 5 9 2 6 5 3 5 8 9 7 9 3 2 3 8 making heap... after make_heap, v: 9 │ 8 9 │ 6 5 8 9 │ 3 5 3 5 3 4 7 2 │ 1 2 3 1 corresponding binary tree is: 9 ┌───────┴───────┐ 8 9 ┌───┴───┐ ┌───┴───┐ 6 5 8 9 ┌─┴─┐ ┌─┴─┐ ┌─┴─┐ ┌─┴─┐ 3 5 3 5 3 4 7 2 ┌┴┐ ┌┴┐ ┌┴┐ ┌┴┐ ┌┴┐ ┌┴┐ ┌┴┐ ┌┴┐ 1 2 3 1

[edit] See also