std::unique_copy
From Cppreference
| Defined in header <algorithm>
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| template< class ForwardIterator, class OutputIterator >
ForwardIterator unique_copy( ForwardIterator first, ForwardIterator last, |
(1) | |
| template< class ForwardIterator, class OutputIterator, class BinaryPredicate >
ForwardIterator unique_copy( ForwardIterator first, ForwardIterator last, |
(2) | |
Copies the elements from the range [first, last), to another range beginning at d_first in such a way, that there are no consecutive equal elements. Only the first element of each group of equal elements is copied. The first version uses operator== to compare the elements, the second version uses the given binary predicate p.
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[edit] Parameters
| first, last | - | the range of elements to process | |||||||||
| d_first | - | the beginning of the destination range | |||||||||
| p | - | binary predicate which returns true if the elements should be treated as equal. The signature of the predicate function should be equivalent to the following:
The signature does not need to have const &, but the function must not modify the objects passed to it. |
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[edit] Return value
output iterator to the element past the last written element
[edit] Equivalent function
| First version |
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template<class ForwardIterator, class OutputIterator> ForwardIterator unique_copy(ForwardIterator first, ForwardIterator last, OutputIterator d_first) { *d_first = *first; while (++first != last) { if (!(*d_first == *first)) { *(++d_first) = *first; } } return ++d_first; } |
| Second version |
template<class ForwardIterator, class OutputIterator, class BinaryPredicate> ForwardIterator unique_copy(ForwardIterator first, ForwardIterator last, OutputIterator d_first, BinaryPredicate p) { *d_first = *first; while (++first != last) { if (!p(*result, *first)) { *(++d_first) = *first; } } return ++d_first; } |
[edit] Example
The following program trims all multiple consecutive spaces in a const string and prints the result
#include <string> #include <iostream> #include <algorithm> #include <iterator> int main() { std::string s1 = "The string with many spaces!"; std::cout << "before: " << s1 << '\n'; std::string s2; std::unique_copy(s1.begin(), s1.end(), std::back_inserter(s2), [](char c1, char c2){ return c1 == ' ' && c2 == ' '; }); std::cout << "after: " << s2 << '\n'; }
Output:
before: The string with many spaces! after: The string with many spaces!
[edit] Complexity
linear in the distance between first and last
[edit] See also
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finds two identical (or some other relationship) items adjacent to each other (function template) |
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removes consecutive duplicate elements in a range (function template) |
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