std::pop_heap
Defined in header
<algorithm>
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template< class RandomIt >
void pop_heap( RandomIt first, RandomIt last ); |
(1) | |
template< class RandomIt, class Compare >
void pop_heap( RandomIt first, RandomIt last, Compare comp ); |
(2) | |
Swaps the value in the position first
and the value in the position last-1
and makes the subrange [first, last-1)
into a max heap. This has the effect of removing the first (largest) element from the heap defined by the range [first, last)
.
The first version of the function uses operator< to compare the elements, the second uses the given comparison function comp
.
Contents |
[edit] Parameters
first, last | - | the range of elements defining the valid nonempty heap to modify |
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); The signature does not need to have const &, but the function object must not modify the objects passed to it. |
Type requirements | ||
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RandomIt must meet the requirements of ValueSwappable and RandomAccessIterator .
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-The type of dereferenced RandomIt must meet the requirements of MoveAssignable and MoveConstructible .
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[edit] Return value
(none)
[edit] Complexity
At most 2×log(N) comparisons where N=std::distance(first, last).
[edit] Notes
A max heap is a range of elements [f,l)
that has the following properties:
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- *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> #include <vector> int main() { std::vector<int> v { 3, 1, 4, 1, 5, 9 }; std::make_heap(v.begin(), v.end()); std::cout << "v: "; for (auto i : v) std::cout << i << ' '; std::cout << '\n'; std::pop_heap(v.begin(), v.end()); // moves the largest to the end std::cout << "after pop_heap: "; for (auto i : v) std::cout << i << ' '; std::cout << '\n'; int largest = v.back(); v.pop_back(); // actually removes the largest element std::cout << "largest element: " << largest << '\n'; std::cout << "heap without largest: "; for (auto i : v) std::cout << i << ' '; std::cout << '\n'; }
Output:
v: 9 5 4 1 1 3 after pop_heap: 5 3 4 1 1 9 largest element: 9 heap without largest: 5 3 4 1 1
[edit] See also
adds an element to a max heap (function template) |
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creates a max heap out of a range of elements (function template) |