std::ranges::is_heap_until

 

C++

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Feature test macros(C++20)

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Concepts library(C++20)

Diagnostics library

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Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

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Numerics library

Date and time library

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Filesystem library(C++17)

Concurrency support library(C++11)

Execution control 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 I is_heap_until( 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> constexprranges::borrowed_iterator_t<R>     is_heap_until( R&& r, Comp comp ={}, Proj proj ={});	(2)	(since C++20)

Within the specified range, finds the longest range which starting from the beginning of the specified range and 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.

Parameters

first, last	-	the range of elements to examine
r	-	the range of elements to examine
pred	-	predicate to apply to the projected elements
proj	-	projection to apply to the elements

Return value

The last iterator iter in the specified range for which:

1) The range [first, iter) is a heap with respect to comp and proj.

2) The range [ranges::begin(r), iter) is a heap with respect to comp and proj.

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_until_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 I operator()(I first, S last, Comp comp ={}, Proj proj ={})const{std::iter_difference_t<I> n{ranges::distance(first, last)}, dad{0}, son{1};for(; son != n;++son){if(std::invoke(comp, std::invoke(proj, *(first + dad)), std::invoke(proj, *(first + son))))return first + son;elseif((son %2)==0)++dad;}return first + n;}   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>constexprranges::borrowed_iterator_t<R> operator()(R&& r, Comp comp ={}, Proj proj ={})const{return(*this)(ranges::begin(r), ranges::end(r), std::move(comp), std::move(proj));}};   inlineconstexpr is_heap_until_fn is_heap_until{};

Example

The example renders a given vector as a (balanced) Binary tree.

Run this code

#include <algorithm>#include <cmath>#include <iostream>#include <iterator>#include <vector>   void out(constauto& what, int n =1){while(n-->0)std::cout<< what;}   void draw_bin_tree(auto first, auto last){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){constint n{1<< t};constint w{(1<<(m - t -1))-1}; bails(n, w), data(n, w, first, last);};   constauto size{std::ranges::distance(first, last)};constint m{static_cast<int>(std::ceil(std::log2(1+ size)))};for(int i{}; i != m;++i) tier(i, m, first, last);}   int main(){std::vector<int> v{3, 1, 4, 1, 5, 9}; std::ranges::make_heap(v);   // probably mess up the heap v.push_back(2); v.push_back(6);   out("v after make_heap and push_back:\n"); draw_bin_tree(v.begin(), v.end());   out("the max-heap prefix of v:\n");constauto heap_end = std::ranges::is_heap_until(v); draw_bin_tree(v.begin(), heap_end);}

Output:

 v after make_heap and push_back: 9 ┌───┴───┐ 5 4 ┌─┴─┐ ┌─┴─┐ 1 1 3 2 ┌┴┐ ┌┴┐ ┌┴┐ ┌┴┐ 6 the max-heap prefix of v: 9 ┌─┴─┐ 5 4 ┌┴┐ ┌┴┐ 1 1 3 2

See also

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