std::make_heap
Defined in header <algorithm>
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template< class RandomAccessIterator > void make_heap( RandomAccessIterator first, RandomAccessIterator last ); |
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template< class RandomAccessIterator, class Compare > void make_heap( RandomAccessIterator first, RandomAccessIterator last, |
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Constructs a 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.
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[edit] Parameters
first, last | - | the range of elements to make the heap from | |||||||||
comp | - | comparison function which returns true if the first argument is less than the second. The signature of the comparison function should be equivalent to the following:
The signature does not need to have const &, but the function must not modify the objects passed to it. |
[edit] Return value
(none)
[edit] Complexity
At most 3*std::distance(first, last) comparisons.
[edit] Notes
A heap is a range of elements [f,l) that has the following properties:
- *f is the largest element in the range
- a new element can be added using std::push_heap()
- the first element can be removed using std::pop_heap()
The actual arrangement of the elements is implementation defined.
[edit] Example
#include <iostream> #include <algorithm> int main() { std::vector<int> v { 3, 1, 4, 1, 5, 9 }; std::cout << "initially, v: "; for (auto i : v) std::cout << i << ' '; std::cout << '\n'; std::make_heap(v.begin(), v.end()); std::cout << "after make_heap, v: "; for (auto i : v) std::cout << i << ' '; std::cout << '\n'; std::pop_heap(v.begin(), v.end()); auto largest = v.back(); v.pop_back(); std::cout << "largest element: " << largest << '\n'; std::cout << "after removing the largest element, v: "; for (auto i : v) std::cout << i << ' '; std::cout << '\n'; }
Output:
initially, v: 3 1 4 1 5 9 after make_heap, v: 9 5 4 1 1 3 largest element: 9 after removing the largest element, v: 5 3 4 1 1
[edit] See also
turns a heap into a sorted range of elements (function template) |