std::partial_sort_copy
| Defined in header <algorithm>
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| template< class InputIt, class RandomIt > RandomIt partial_sort_copy( InputIt first, InputIt last, |
(1) | |
| template< class ExecutionPolicy, class ForwardIt, class RandomIt > RandomIt partial_sort_copy( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, |
(2) | (since C++17) |
| template< class InputIt, class RandomIt, class Compare > RandomIt partial_sort_copy( InputIt first, InputIt last, |
(3) | |
| template< class ExecutionPolicy, class ForwardIt, class RandomIt, class Compare > RandomIt partial_sort_copy( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, |
(4) | (since C++17) |
Sorts some of the elements in the range [first, last) in ascending order, storing the result in the range [d_first, d_last).
At most d_last - d_first of the elements are moved to the range [d_first, d_first + n) and then sorted. n is the number of elements to sort (n = min(last - first, d_last - d_first)). The order of equal elements is not guaranteed to be preserved.
operator<.comp.policy. This overload only participates in overload resolution if std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is trueContents |
[edit] Parameters
| first, last | - | the range of elements to sort |
| d_first, d_last | - | random access iterators defining the destination range |
| 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 (i.e. is ordered before) 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 | ||
-InputIt must meet the requirements of InputIterator.
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-ForwardIt must meet the requirements of ForwardIterator.
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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
an iterator to the element defining the upper boundary of the sorted range, i.e. d_first + min(last - first, d_last - d_first).
[edit] Complexity
O(N·log(min(D,N)), where N = std::distance(first, last), D = std::distance(d_first, d_last) applications of cmp.
[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
ExecutionPolicyis one of the three standard policies, std::terminate is called. For any otherExecutionPolicy, the behavior is implementation-defined. - If the algorithm fails to allocate memory, std::bad_alloc is thrown.
[edit] Example
The following code sorts a vector of integers and copies them into a smaller and a larger vector.
#include <algorithm> #include <vector> #include <functional> #include <iostream> int main() { std::vector<int> v0{4, 2, 5, 1, 3}; std::vector<int> v1{10, 11, 12}; std::vector<int> v2{10, 11, 12, 13, 14, 15, 16}; std::vector<int>::iterator it; it = std::partial_sort_copy(v0.begin(), v0.end(), v1.begin(), v1.end()); std::cout << "Writing to the smaller vector in ascending order gives: "; for (int a : v1) { std::cout << a << " "; } std::cout << '\n'; if(it == v1.end()) std::cout << "The return value is the end iterator\n"; it = std::partial_sort_copy(v0.begin(), v0.end(), v2.begin(), v2.end(), std::greater<int>()); std::cout << "Writing to the larger vector in descending order gives: "; for (int a : v2) { std::cout << a << " "; } std::cout << '\n' << "The return value is the iterator to " << *it << '\n'; }
Output:
Writing to the smaller vector in ascending order gives: 1 2 3 The return value is the end iterator Writing to the larger vector in descending order gives: 5 4 3 2 1 15 16 The return value is the iterator to 15
[edit] See also
| sorts the first N elements of a range (function template) | |
| sorts a range into ascending order (function template) | |
| sorts a range of elements while preserving order between equal elements (function template) |