std::remove_copy

Defined in header <algorithm>

template< class InputIt, class OutputIt, class T >
OutputIt remove_copy( InputIt first, InputIt last, OutputIt d_first,
                      const T& value );

(1)

template< class InputIt, class OutputIt, class UnaryPredicate >
OutputIt remove_copy_if( InputIt first, InputIt last, OutputIt d_first,
                         UnaryPredicate p );

(2)

Copies elements from the range [first, last), to another range beginning at d_first, omitting the elements which satisfy specific criteria. The first version ignores the elements that are equal to value, the second version ignores the elements for which predicate p returns true. Source and destination ranges cannot overlap.

Parameters

first, last	-	the range of elements to copy
d_first	-	the beginning of the destination range.
value	-	the value of the elements not to copy
Type requirements
- `InputIt` must meet the requirements of `InputIterator`.
- `OutputIt` must meet the requirements of `OutputIterator`.
- `UnaryPredicate` must meet the requirements of `Predicate`.

Return value

Iterator to the element past the last element copied.

Complexity

Exactly last - first applications of the predicate.

Possible implementation

First version

template<class InputIt, class OutputIt, class T>
OutputIt remove_copy(InputIt first, InputIt last,
                     OutputIt d_first, const T& value)
{
    for (; first != last; ++first) {
        if (!(*first == value)) {
            *d_first++ = *first;
        }
    }
    return d_first;
}

Second version

template<class InputIt, class OutputIt, class UnaryPredicate>
OutputIt remove_copy_if(InputIt first, InputIt last,
                        OutputIt d_first, UnaryPredicate p)
{
    for (; first != last; ++first) {
        if (!p(*first)) {
            *d_first++ = *first;
        }
    }
    return d_first;
}

Example

The following code outputs a string while erasing the spaces on the fly.

#include <algorithm>
#include <iterator>
#include <string>
#include <iostream>
int main()
{
    std::string str = "Text with some   spaces";
    std::cout << "before: " << str << "\n";
  
    std::cout << "after:  ";
    std::remove_copy(str.begin(), str.end(),
                     std::ostream_iterator<char>(std::cout), ' ');
    std::cout << '\n';
}

Output:

before: Text with some   spaces
after:  Textwithsomespaces

removeremove_if	removes elements satisfying specific criteria (function template)
copycopy_if (C++11)	copies a range of elements to a new location (function template)
std::experimental::parallel::remove_copy (parallelism TS)	parallelized version of `std::remove_copy` (function template)
std::experimental::parallel::remove_copy_if (parallelism TS)	parallelized version of `std::remove_copy_if` (function template)

Links:

http://en.cppreference.com/w/cpp/algorithm/remove_copy

doc_CPP

2025-01-10 15:47:30

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