std::partition_copy
Defined in header
<algorithm>
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template< class InputIt, class OutputIt1,
class OutputIt2, class UnaryPredicate > |
(since C++11) | |
Copies the elements from the range [first, last)
to two different ranges depending on the value returned by the predicate p
. The elements, that satisfy the predicate p
, are copied to the range beginning at d_first_true
. The rest of the elements are copied to the range beginning at d_first_false
.
The behavior is undefined if the input range overlaps either of the output ranges.
Contents |
[edit] Parameters
first, last | - | the range of elements to sort |
d_first_true | - | the beginning of the output range for the elements that satisfy p |
d_first_false | - | the beginning of the output range for the elements that do not satisfy p |
p | - | unary predicate which returns true if the element should be placed in d_first_true. The signature of the predicate function should be equivalent to the following: bool pred(const Type &a); The signature does not need to have const &, but the function must not modify the objects passed to it. |
Type requirements | ||
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InputIt must meet the requirements of InputIterator .
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-The type of dereferenced InputIt must meet the requirements of CopyAssignable .
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OutputIt1 must meet the requirements of OutputIterator .
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OutputIt2 must meet the requirements of OutputIterator .
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UnaryPredicate must meet the requirements of Predicate .
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[edit] Return value
A pair constructed from the iterator to the end of the d_first_true
range and the iterator to the end of the d_first_false
range.
[edit] Complexity
Exactly distance(first, last)
applications of p
.
[edit] Possible implementation
template<class InputIt, class OutputIt1, class OutputIt2, class UnaryPredicate> std::pair<OutputIt1, OutputIt2> partition_copy(InputIt first, InputIt last, OutputIt1 d_first_true, OutputIt2 d_first_false, UnaryPredicate p) { while (first != last) { if (p(*first)) { *d_first_true = *first; ++d_first_true; } else { *d_first_false = *first; ++d_first_false; } ++first; } return std::pair<OutputIt1, OutputIt2>(d_first_true, d_first_false); } |
[edit] Example
#include <iostream> #include <algorithm> #include <utility> int main() { int arr [10] = {1,2,3,4,5,6,7,8,9,10}; int true_arr [5] = {0}; int false_arr [5] = {0}; std::partition_copy(std::begin(arr), std::end(arr), std::begin(true_arr),std::begin(false_arr), [] (int i) {return i > 5;}); std::cout << "true_arr: "; for (auto it = std::begin(true_arr); it != std::end(true_arr); ++it) { std::cout << *it << ' '; } std::cout << '\n'; std::cout << "false_arr: "; for (auto it = std::begin(false_arr); it != std::end(false_arr); ++it) { std::cout << *it << ' '; } std::cout << '\n'; return 0; }
Output:
true_arr: 6 7 8 9 10 false_arr: 1 2 3 4 5
[edit] See also
divides a range of elements into two groups (function template) |
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divides elements into two groups while preserving their relative order (function template) |
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(parallelism TS)
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parallelized version of std::partition_copy (function template) |