Home Original page

std::ranges::make_heap - cppreference.com

Defined in header <algorithm>

Call signature

template< std::random_access_iterator I, std::sentinel_for<I> S, class Comp = ranges::less, class Proj = std::identity > requires std::sortable<I, Comp, Proj> constexpr I make_heap( I first, S last, Comp comp = {}, Proj proj = {} );

 (1) (since C++20)

template< ranges::random_access_range R, class Comp = ranges::less, class Proj = std::identity > requires std::sortable<ranges::iterator_t<R>, Comp, Proj> constexpr ranges::borrowed_iterator_t<R> make_heap( R&& r, Comp comp = {}, Proj proj = {} );

 (2) (since C++20)

Constructs a heap with respect to comp and proj from the elements in the specified range.

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:

Parameters

first, last - the iterator-sentinel pair defining the range of elements to modify
r - the range of elements to modify
comp - comparator to apply to the projected elements
proj - projection to apply to the elements

Return value

1) last

2) ranges::end(r)

Complexity

At most 3·N applications of comp and 6·N applications of proj, where N is:

1) ranges::distance(first, last)

2) ranges::distance(r)

Example

#include <algorithm>
#include <cmath>
#include <functional>
#include <iostream>
#include <vector>

void out(const auto& what, int n = 1)
{
    while (n-- > 0)
        std::cout << what;
}

void print(auto rem, const auto& v)
{
    out(rem);
    for (auto e : v)
        out(e), out(' ');
    out('\n');
}

void draw_heap(const auto& v)
{
    auto bails = [](int n, int w)
    {
        auto b = [](int w) { out("┌"), out("─", w), out("┴"), out("─", w), out("┐"); };
        if (!(n /= 2))
            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 h{1, 6, 1, 8, 0, 3, 3, 9, 8, 8, 7, 4, 9, 8, 9};
    print("source: ", h);
    
    std::ranges::make_heap(h);
    print("\n" "max-heap: ", h);
    draw_heap(h);
    
    std::ranges::make_heap(h, std::greater{});
    print("\n" "min-heap: ", h);
    draw_heap(h);
}

Output: 

source: 1 6 1 8 0 3 3 9 8 8 7 4 9 8 9

max-heap: 9 8 9 8 8 4 9 6 1 0 7 1 3 8 3
       9
   ┌───┴───┐
   8       9
 ┌─┴─┐   ┌─┴─┐
 8   8   4   9
┌┴┐ ┌┴┐ ┌┴┐ ┌┴┐
6 1 0 7 1 3 8 3

min-heap: 0 1 1 8 6 3 3 9 8 8 7 4 9 8 9
       0
   ┌───┴───┐
   1       1
 ┌─┴─┐   ┌─┴─┐
 8   6   3   3
┌┴┐ ┌┴┐ ┌┴┐ ┌┴┐
9 8 8 7 4 9 8 9

See also

checks if the given range is a max heap
(algorithm function object)[edit]
finds the largest subrange that is a max heap
(algorithm function object)[edit]
adds an element to a max heap
(algorithm function object)[edit]
removes the largest element from a max heap
(algorithm function object)[edit]
turns a max heap into a range of elements sorted in ascending order
(algorithm function object)[edit]
creates a max heap out of a range of elements
(function template) [edit]