std::make_heap

 

C++

Compiler support

Freestanding and hosted

Language

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)

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
all_ofany_ofnone_of (C++11)(C++11)(C++11) for_each for_each_n (C++17)	countcount_if mismatch equal adjacent_find	search search_n lexicographical_compare lexicographical_compare_three_way (C++20)	findfind_iffind_if_not (C++11) find_end find_first_of
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) shift_leftshift_right (C++20)(C++20) transform	fill fill_n generate generate_n swap iter_swap swap_ranges sample (C++17)	removeremove_if replacereplace_if reverse rotate unique random_shuffle (until C++17)	remove_copyremove_copy_if replace_copyreplace_copy_if reverse_copy rotate_copy unique_copy shuffle (C++11)
Partitioning operations
is_partitioned (C++11) partition_point (C++11)	partition partition_copy (C++11)	stable_partition
Sorting operations
is_sorted (C++11) is_sorted_until (C++11)	sort stable_sort	partial_sort partial_sort_copy	nth_element
Binary search operations
lower_bound	upper_bound	binary_search	equal_range
Set operations (on sorted ranges)
merge inplace_merge	set_difference set_intersection	set_symmetric_difference set_union	includes
Heap operations
is_heap (C++11) is_heap_until (C++11)	make_heap sort_heap	push_heap pop_heap
Minimum/maximum operations
max max_element	min min_element	minmax (C++11) minmax_element (C++11)	clamp (C++17)
Permutations
is_permutation (C++11)	next_permutation	prev_permutation
Numeric operations
iota (C++11) inner_product adjacent_difference	accumulate reduce (C++17) transform_reduce (C++17)	transform_inclusive_scan (C++17) transform_exclusive_scan (C++17)	partial_sum inclusive_scan (C++17) exclusive_scan (C++17)
Operations on uninitialized storage
uninitialized_copy uninitialized_move (C++17) uninitialized_fill	uninitialized_copy_n (C++11) uninitialized_move_n (C++17) uninitialized_fill_n	uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17)	destroy (C++17) destroy_n (C++17) destroy_at (C++17) construct_at (C++20)
C library
qsort	bsearch

 

Defined in header <algorithm>
	(1)
template< class RandomIt > void make_heap( RandomIt first, RandomIt last );			(until C++20)
template< class RandomIt > constexpr void make_heap( RandomIt first, RandomIt last );			(since C++20)
		(2)
template< class RandomIt, class Compare > void make_heap( RandomIt first, RandomIt last,                 Compare comp );				(until C++20)
template< class RandomIt, class Compare > constexpr void make_heap( RandomIt first, RandomIt last,                           Compare comp );				(since C++20)

Constructs a max heap in the range [first, last). The first version of the function uses operator< to compare the elements, the second uses the given comparison function comp.

Parameters

first, last	-	the range of elements to make the heap from
comp	-	comparison function object (i.e. an object that satisfies the requirements of Compare) which returns ​true if the first argument is less than the second. The signature of the comparison function should be equivalent to the following:  bool cmp(const Type1 &a, const Type2 &b); While the signature does not need to have const &, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1 & is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy (since C++11)). The types Type1 and Type2 must be such that an object of type RandomIt can be dereferenced and then implicitly converted to both of them. ​
Type requirements
- RandomIt must meet the requirements of LegacyRandomAccessIterator.
- The type of dereferenced RandomIt must meet the requirements of MoveAssignable and MoveConstructible.

Return value

(none)

Complexity

At most 3*std::distance(first, last) comparisons.

Notes

A max heap is a range of elements [f,l) that has the following properties:

• With N = l-f, for all 0 < i < N, f[(i-1)/2] does not compare less than f[i].
• A new element can be added using std::push_heap, in \(\scriptsize \mathcal{O}(\log N)\)𝓞(log N) time.
• The first element can be removed using std::pop_heap, in \(\scriptsize \mathcal{O}(\log N)\)𝓞(log N) time.

Example

Run this code

#include <algorithm>
#include <functional>
#include <iostream>
#include <string_view>
#include <vector>
 
void print(std::string_view text, std::vector<int> const& v = {}) {
    std::cout << text << ": ";
    for (const auto& e : v) std::cout << e << ' ';
    std::cout << '\n';
}
 
int main()
{
    print("Max heap");
 
    std::vector<int> v { 3, 2, 4, 1, 5, 9 };
    print("initially, v", v);
 
    std::make_heap(v.begin(), v.end());
    print("after make_heap, v", v);
 
    std::pop_heap(v.begin(), v.end());
    print("after pop_heap, v", v);
 
    auto top = v.back();
    v.pop_back();
    print("former top element", {top});
    print("after removing the former top element, v", v);
 
    print("\nMin heap");
 
    std::vector<int> v1 { 3, 2, 4, 1, 5, 9 };
    print("initially, v1", v1);
 
    std::make_heap(v1.begin(), v1.end(), std::greater<>{});
    print("after make_heap, v1", v1);
 
    std::pop_heap(v1.begin(), v1.end(), std::greater<>{});
    print("after pop_heap, v1", v1);
 
    auto top1 = v1.back();
    v1.pop_back();
    print("former top element", {top1});
    print("after removing the former top element, v1", v1);
}

Output:

Max heap:
initially, v: 3 2 4 1 5 9 
after make_heap, v: 9 5 4 1 2 3 
after pop_heap, v: 5 3 4 1 2 9 
former top element: 9
after removing the former top element, v: 5 3 4 1 2 
 
Min heap:
initially, v1: 3 2 4 1 5 9 
after make_heap, v1: 1 2 4 3 5 9 
after pop_heap, v1: 2 3 4 9 5 1 
former top element: 1
after removing the former top element, v1: 2 3 4 9 5

See also

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