std::ranges::is_heap

 

C++

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Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Algorithm library

Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
is_execution_policy (C++17)   execution::seqexecution::parexecution::par_unseqexecution::unseq (C++17)    (C++17)(C++17)(C++20)	execution::sequenced_policyexecution::parallel_policyexecution::parallel_unsequenced_policyexecution::parallel_unsequenced (C++17)(C++17)(C++17)(C++20)
Non-modifying sequence operations Batch operations for_each for_each_n (C++17) Search operations all_ofany_ofnone_of (C++11)                (C++11)(C++11) countcount_if mismatch equal findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n Modifying sequence operations Copy operations copycopy_if (C++11) copy_backward copy_n (C++11) move (C++11) move_backward (C++11) Swap operations swap iter_swap swap_ranges Transformation operations replacereplace_if transform replace_copyreplace_copy_if Generation operations fill fill_n generate generate_n Removing operations removeremove_if unique remove_copyremove_copy_if unique_copy Order-changing operations reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) shift_leftshift_right (C++20)(C++20) Sampling operations sample (C++17)	Sorting and related operations Partitioning operations partition partition_copy (C++11)   stable_partition is_partitioned (C++11) partition_point (C++11) Sorting operations sort stable_sort partial_sort partial_sort_copy is_sorted (C++11) is_sorted_until (C++11) nth_element Binary search operations (on partitioned ranges) lower_bound upper_bound equal_range binary_search Set operations (on sorted ranges) includes set_union set_intersection set_difference set_symmetric_difference Merge operations (on sorted ranges) merge inplace_merge Heap operations push_heap pop_heap make_heap sort_heap is_heap (C++11) is_heap_until (C++11) Minimum/maximum operations max min minmax (C++11) clamp (C++17) max_element min_element minmax_element (C++11) Lexicographical comparison operations lexicographical_compare lexicographical_compare_three_way (C++20) Permutation operations next_permutation prev_permutation is_permutation (C++11) C library qsort bsearch
Numeric operations
iota (C++11) inner_product adjacent_difference    accumulate reduce (C++17) transform_reduce (C++17)	partial_sum inclusive_scan (C++17)    exclusive_scan (C++17) transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)
Operations on uninitialized memory
uninitialized_copy uninitialized_move (C++17)    uninitialized_fill uninitialized_copy_n (C++11) uninitialized_move_n (C++17) uninitialized_fill_n	destroy (C++17) destroy_n (C++17) destroy_at (C++17) construct_at (C++20)       uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17)

 

Constrained algorithms

All names in this menu belong to namespace std::ranges

Non-modifying sequence operations

all_ofany_ofnone_of for_each for_each_n    countcount_if adjacent_find mismatch equal lexicographical_compare    containscontains_subrange (C++23)(C++23) findfind_iffind_if_not find_lastfind_last_iffind_last_if_not (C++23)(C++23)(C++23)   find_end find_first_of search search_n starts_with (C++23) ends_with (C++23)

Modifying sequence operations

copycopy_if copy_n copy_backward    move move_backward shift_leftshift_right (C++23)(C++23)   fill fill_n generate generate_n    transform swap_ranges    shuffle sample removeremove_if replacereplace_if reverse rotate remove_copyremove_copy_if    unique replace_copyreplace_copy_if reverse_copy rotate_copy unique_copy

Partitioning operations

is_partitioned    partition_point    partition    partition_copy    stable_partition

Sorting operations

is_sorted is_sorted_until     sort stable_sort         partial_sort       nth_element partial_sort_copy

Binary search operations (on sorted ranges)

lower_bound         upper_bound         binary_search      equal_range

Set operations (on sorted ranges)

merge inplace_merge       set_difference set_intersection    set_union          includes set_symmetric_difference

Heap operations

is_heap is_heap_until       make_heap           sort_heap push_heap pop_heap

Minimum/maximum operations

max max_element         min min_element         minmax minmax_element     clamp

Permutation operations

is_permutation      next_permutation    prev_permutation

Fold operations

fold_left (C++23) fold_left_first (C++23)   fold_right (C++23) fold_right_last (C++23)   fold_left_with_iter (C++23) fold_left_first_with_iter (C++23)

Numeric operations iota (C++23)             Random number generation generate_random (C++26)

Operations on uninitialized storage

construct_at    destroy destroy_n destroy_at uninitialized_copy    uninitialized_move uninitialized_fill uninitialized_copy_n    uninitialized_move_n uninitialized_fill_n uninitialized_default_construct uninitialized_default_construct_n uninitialized_value_construct uninitialized_value_construct_n

Return types

in_fun_result in_in_result in_found_result    in_out_result in_in_out_result    in_out_out_result    min_max_result out_value_result (C++23) in_value_result (C++23)

 

Defined in header <algorithm>
Call signature
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)	(since C++20)
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)	(since C++20)

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 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.

In practice, they may be implemented as function objects, or with special compiler extensions.

Parameters

first, last	-	the iterator and sentinel designating the range of elements to examine
r	-	the range of elements to examine
comp	-	comparator to apply to the projected elements
proj	-	projection to apply to the elements

Return value

1) ranges::is_heap_until(first, last, comp, proj) == last

2) ranges::is_heap_until(r, comp, proj) == ranges::end(r)

Complexity

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

1) ranges::distance(first, last)

2) ranges::distance(r)

Possible implementation

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{};

Example

Run this code

#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);
}

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

See also

ranges::is_heap_until (C++20)	finds the largest subrange that is a max heap (niebloid)
ranges::make_heap (C++20)	creates a max heap out of a range of elements (niebloid)
ranges::push_heap (C++20)	adds an element to a max heap (niebloid)
ranges::pop_heap (C++20)	removes the largest element from a max heap (niebloid)
ranges::sort_heap (C++20)	turns a max heap into a range of elements sorted in ascending order (niebloid)
is_heap (C++11)	checks if the given range is a max heap (function template)