Difference between revisions of "cpp/algorithm/is heap until"

Latest revision as of 19:40, 8 April 2024

Defined in header `<algorithm>`
template< class RandomIt > RandomIt is_heap_until( RandomIt first, RandomIt last );	(1)	(since C++11) (constexpr since C++20)
template< class ExecutionPolicy, class RandomIt > RandomIt is_heap_until( ExecutionPolicy&& policy, RandomIt first, RandomIt last );	(2)	(since C++17)
template< class RandomIt, class Compare > RandomIt is_heap_until( RandomIt first, RandomIt last, Compare comp );	(3)	(since C++11) (constexpr since C++20)
template< class ExecutionPolicy, class RandomIt, class Compare > RandomIt is_heap_until( ExecutionPolicy&& policy, RandomIt first, RandomIt last, Compare comp );	(4)	(since C++17)

Examines the range [first, last) and finds the largest range beginning at first which is a heap.

1) The heap property to be checked is with respect to operator<(until C++20)std::less{}(since C++20).

3) The heap property to be checked is with respect to comp.

2,4) Same as (1,3), but executed according to policy.

These overloads participate in overload resolution only if

std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is true.	(until C++20)
std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> is true.	(since C++20)

first, last	-	the range of elements to examine
policy	-	the execution policy to use. See execution policy for details.
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) `Type1` and `Type2` regardless of value category (thus, Type1& is not allowed, nor is Type1 unless for `Type1` a move is equivalent to a copy(since C++11)). The types Type1 and Type2 must be such that an object of type RandomIt can be dereferenced and then implicitly converted to both of them.
Type requirements
- `RandomIt` must meet the requirements of LegacyRandomAccessIterator.
- `Compare` must meet the requirements of Compare.

[edit] Return value

The last iterator it for which range [first, it) is a heap.

[edit] Complexity

Given $\scriptsize N$ $N$ as std::distance(first, last):

1,2)

O(N)

comparisons using operator<(until C++20)std::less{}(since C++20).

3,4)

O(N)

applications of the comparison function comp.

[edit] Exceptions

The overloads with a template parameter named ExecutionPolicy report errors as follows:

If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
If the algorithm fails to allocate memory, std::bad_alloc is thrown.

[edit] Example

Run this code

#include <algorithm>
#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v{3, 1, 4, 1, 5, 9};
 
    std::make_heap(v.begin(), v.end());
 
    // probably mess up the heap
    v.push_back(2);
    v.push_back(6);
 
    auto heap_end = std::is_heap_until(v.begin(), v.end());
 
    std::cout << "all of v:  ";
    for (const auto& i : v)
        std::cout << i << ' ';
    std::cout << '\n';
 
    std::cout << "only heap: ";
    for (auto i = v.begin(); i != heap_end; ++i)
        std::cout << *i << ' ';
    std::cout << '\n';
}

Output:

all of v:  9 5 4 1 1 3 2 6
only heap: 9 5 4 1 1 3 2

[edit] See also

is_heap (C++11)	checks if the given range is a max heap (function template) [edit]
make_heap	creates a max heap out of a range of elements (function template) [edit]
push_heap	adds an element to a max heap (function template) [edit]
pop_heap	removes the largest element from a max heap (function template) [edit]
sort_heap	turns a max heap into a range of elements sorted in ascending order (function template) [edit]
ranges::is_heap_until (C++20)	finds the largest subrange that is a max heap (niebloid)[edit]

@@ Line 1: / Line 1: @@
 {{cpp/title|is_heap_until}}
-{{cpp/algorithm/sidebar}}
+{{cpp/algorithm/navbar}}
-{{ddcl list begin}}
+{{dcl begin}}
-{{ddcl list header | algorithm}}
+{{dcl header|algorithm}}
-{{ddcl list item | num=1 | notes={{mark c++0x feature}} |
+{{dcl|num=1|since=c++11|notes={{mark constexpr since c++20}}|
-template< class RandomAccessIterator >
+template< class RandomIt >
-RandomAccessIterator is_heap_until( RandomAccessIterator first,
+RandomIt is_heap_until( RandomIt first, RandomIt last );
-                                    RandomAccessIterator last );
 }}
-{{ddcl list item | num=2 | notes={{mark c++0x feature}} |
+{{dcl|num=2|since=c++17|
-template< class RandomAccessIterator, class Compare >
+template< class ExecutionPolicy, class RandomIt >
-RandomAccessIterator is_heap_until( RandomAccessIterator first,
+RandomIt is_heap_until( ExecutionPolicy&& policy,
-                                    RandomAccessIterator last,
+                        RandomIt first, RandomIt last );
-                                    Compare comp );
 }}
-{{ddcl list end}}
+{{dcl|num=3|since=c++11|notes={{mark constexpr since c++20}}|
+template< class RandomIt, class Compare >
+RandomIt is_heap_until( RandomIt first, RandomIt last, Compare comp );
+}}
+{{dcl|num=4|since=c++17|
+template< class ExecutionPolicy, class RandomIt, class Compare >
+RandomIt is_heap_until( ExecutionPolicy&& policy,
+                        RandomIt first, RandomIt last, Compare comp );
+}}
+{{dcl end}}
-Examines the range {{tt|[first, last)}} and finds the largest range beginning at {{tt|first}} which is ''heap''. The first version of the function uses {{cpp|operator<}} to compare the elements, the second uses the given comparison function {{tt|comp}}.
+Examines the range {{range|first|last}} and finds the largest range beginning at {{c|first}} which is a {{rlp|/#Heap operations|heap}}.
-<!-- ======== -->
+@1@ The heap property to be checked is with respect to {{rev inl|until=c++20|{{c/core|operator<}}}}{{rev inl|since=c++20|{{c|std::less{}<!---->}}}}.
-{{params}}
-{{param list begin}}
-{{param list item | first, last | the range of elements to examine}}
-{{param list cmp | comp | p1=RandomAccessIterator}}
-{{param list end}}
-<!-- ======== -->
+@3@ The heap property to be checked is with respect to {{c|comp}}.
-{{returns}}
-The upper bound of the largest range beginning at {{tt|first}} which is ''heap''. That is, the last iterator {{tt|it}] for which range {{tt|[first, it)}} is ''heap''.
-<!-- ======== -->
+@2,4@ Same as {{v|1,3}}, but executed according to {{c|policy}}.
-{{complex}}
+@@ {{cpp/algorithm/parallel overload precondition|plural=yes}}
-linear in the distance between {{tt|first}} and {{tt|last}}
+===Parameters===
+{{par begin}}
+{{par|first, last|the range of elements to examine}}
+{{par exec pol}}
+{{par cmp|comp|p1=RandomIt}}
+{{par hreq}}
+{{par req named|RandomIt|RandomAccessIterator}}
+{{par req named|Compare|Compare}}
+{{par end}}
-<!-- ======== -->
+===Return value===
-{{example}}
+The last iterator {{c|it}} for which range {{range|first|it}} is a heap.
-{{example cpp
- |
- | code=
- | output=
-}}
-<!-- ======== -->
+===Complexity===
-===Notes===
+Given {{mathjax-or|\(\scriptsize N\)|N}} as {{c|std::distance(first, last)}}:
-{{cpp/algorithm/notes heap}}
+@1,2@ {{mathjax-or|\(\scriptsize O(N)\)|O(N)}} comparisons using {{rev inl|until=c++20|{{c/core|operator<}}}}{{rev inl|since=c++20|{{c|std::less{}<!---->}}}}.
+@3,4@ {{mathjax-or|\(\scriptsize O(N)\)|O(N)}} applications of the comparison function {{c|comp}}.
+===Exceptions===
+{{cpp/algorithm/parallel exceptions reporting behavior|singular=no}}
+===Example===
+{{example
+|code=
+#include <algorithm>
+#include <iostream>
+#include <vector>
+int main()
+{
+    std::vector<int> v{3, 1, 4, 1, 5, 9};
+    std::make_heap(v.begin(), v.end());
+    // probably mess up the heap
+    v.push_back(2);
+    v.push_back(6);
+    auto heap_end = std::is_heap_until(v.begin(), v.end());
+    std::cout << "all of v:  ";
+    for (const auto& i : v)
+        std::cout << i << ' ';
+    std::cout << '\n';
+    std::cout << "only heap: ";
+    for (auto i = v.begin(); i != heap_end; ++i)
+        std::cout << *i << ' ';
+    std::cout << '\n';
+}
+|output=
+all of v:  9 5 4 1 1 3 2 6
+only heap: 9 5 4 1 1 3 2
+}}
-<!-- ======== -->
+===See also===
-{{see also}}
+{{dsc begin}}
-{{dcl list begin}}
+{{dsc inc|cpp/algorithm/dsc is_heap}}
-{{dcl list template | cpp/algorithm/dcl list is_heap}}
+{{dsc inc|cpp/algorithm/dsc make_heap}}
-{{dcl list end}}
+{{dsc inc|cpp/algorithm/dsc push_heap}}
+{{dsc inc|cpp/algorithm/dsc pop_heap}}
+{{dsc inc|cpp/algorithm/dsc sort_heap}}
+{{dsc inc|cpp/algorithm/ranges/dsc is_heap_until}}
+{{dsc end}}
-<!-- Language links go here -->
+{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
-{{lang}}

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Difference between revisions of "cpp/algorithm/is heap until"

Latest revision as of 19:40, 8 April 2024

Contents

[edit] Parameters

[edit] Return value

[edit] Complexity

[edit] Exceptions

[edit] Example

[edit] See also

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