std::sort_heap
Defined in header <algorithm>
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(1) | ||
template< class RandomIt > void sort_heap( RandomIt first, RandomIt last ); |
(until C++20) | |
template< class RandomIt > constexpr void sort_heap( RandomIt first, RandomIt last ); |
(since C++20) | |
(2) | ||
template< class RandomIt, class Compare > void sort_heap( RandomIt first, RandomIt last, Compare comp ); |
(until C++20) | |
template< class RandomIt, class Compare > constexpr void sort_heap( RandomIt first, RandomIt last, Compare comp ); |
(since C++20) | |
Converts the max heap [first, last)
into a sorted range in ascending order. The resulting range no longer has the heap property.
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 sort |
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) |
Type requirements | ||
-RandomIt must meet the requirements of ValueSwappable and LegacyRandomAccessIterator.
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-The type of dereferenced RandomIt must meet the requirements of MoveAssignable and MoveConstructible.
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Return value
(none)
Complexity
At most 2×N×log(N) comparisons where N=std::distance(first, last).
Notes
A max heap is a range of elements [f,l)
that has the following properties:
- With
N = l - f
, for all0 < i < N
,f[floor(
does not compare less than
)]i-1 2 f[i]
. - a new element can be added using std::push_heap()
- the first element can be removed using std::pop_heap()
- With
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 2444 | C++98 | complexity requirement was wrong by a factor of 2 | corrected |
Possible implementation
First version |
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template< class RandomIt > void sort_heap( RandomIt first, RandomIt last ) { while (first != last) std::pop_heap(first, last--); } |
Second version |
template< class RandomIt, class Compare > void sort_heap( RandomIt first, RandomIt last, Compare comp ) { while (first != last) std::pop_heap(first, last--, comp); } |
Example
#include <algorithm> #include <vector> #include <iostream> int main() { std::vector<int> v = {3, 1, 4, 1, 5, 9}; std::make_heap(v.begin(), v.end()); std::cout << "heap:\t"; for (const auto &i : v) { std::cout << i << ' '; } std::sort_heap(v.begin(), v.end()); std::cout << "\nsorted:\t"; for (const auto &i : v) { std::cout << i << ' '; } std::cout << '\n'; }
Output:
heap: 9 4 5 1 1 3 sorted: 1 1 3 4 5 9
See also
creates a max heap out of a range of elements (function template) |