std::ranges::is_heap
来自 zh.cppreference.net
| 定义于头文件 <algorithm>
|
||
| 调用签名 |
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template< std::random_access_iterator I, std::sentinel_for<I> S,
class Proj = std::identity,
std::indirect_strict_weak_order
<std::projected<I, Proj>> Comp = ranges::less >
constexpr bool is_heap( I first, S last, Comp comp = {}, Proj proj = {} );
|
(1) | (自C++20起) |
template< ranges::random_access_range R, class Proj = std::identity,
std::indirect_strict_weak_order
<std::projected
<ranges::iterator_t<R>, Proj>> Comp = ranges::less >
constexpr bool is_heap( R&& r, Comp comp = {}, Proj proj = {} );
|
(2) | (自C++20起) |
检查指定范围是否表示一个堆，相对于comp和proj。
1) 指定范围是
[first, last)。2) 指定范围是
r。此页面上描述的类似函数的实体是算法函数对象（非正式地称为niebloids），即：
参数
| first, last | - | 定义待检查元素范围的 迭代器-哨位对 |
| r | - |
待检查元素的
range
范围
|
| comp | - | 应用于投影元素的比较器 |
| proj | - | 应用于元素的投影 |
返回值
1)
ranges::
is_heap_until
(
first, last, comp, proj
)
==
last
2)
ranges::
is_heap_until
(
r, comp, proj
)
==
ranges::
end
(
r
)
复杂度
O(N) 次 comp 和 proj 的应用，其中 N 为：
1)
ranges::
distance
(
first, last
)
2)
ranges::
distance
(
r
)
可能的实现
struct is_heap_fn { template<std::random_access_iterator I, std::sentinel_for<I> 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<R>, 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{}; |
示例
运行此代码
#include <algorithm> #include <bit> #include <cmath> #include <iostream> #include <vector> 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<int>(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<int> 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); }
输出：
初始状态，v： 3 1 4 1 5 9 2
参阅
(C++20) |
找到作为最大堆的最大子范围 (算法函数对象) |
(C++20) |
从一个范围元素创建最大堆 (算法函数对象) |
(C++20) |
向最大堆添加元素 (算法函数对象) |
(C++20) |
从最大堆移除最大元素 (算法函数对象) |
(C++20) |
将最大堆转换为元素的有序范围 (算法函数对象) |
(C++11) |
检查给定范围是否为最大堆 (函数模板) |