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 | ||
-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) | |
| divides elements into two groups while preserving their relative order (function template) |