std::ranges::make_heap
From cppreference.com
| Defined in header <algorithm>
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| Call signature |
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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:
- 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 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)
last2)
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
Run this code
#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