std::unique_copy

 

C++

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Utilities library

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Algorithms library

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Input/output library

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Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Algorithm library

Functions
Non-modifying sequence operations
all_ofany_ofnone_of (C++11)(C++11)(C++11) for_each countcount_if mismatch equal	findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n removeremove_if remove_copyremove_copy_if	replacereplace_if replace_copyreplace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) unique unique_copy
Partitioning operations
is_partitioned (C++11) partition partition_copy (C++11)	stable_partition partition_point (C++11)
Sorting operations (on sorted ranges)
is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
Binary search operations (on sorted ranges)
lower_bound upper_bound	binary_search equal_range
Set operations (on sorted ranges)
merge inplace_merge includes	set_difference set_intersection set_symmetric_difference set_union
Heap operations
is_heap (C++11) is_heap_until (C++11) make_heap	push_heap pop_heap sort_heap
Minimum/maximum operations
max max_element min min_element minmax (C++11) minmax_element (C++11)	lexicographical_compare is_permutation (C++11) next_permutation prev_permutation
Numeric operations
iota (C++11) accumulate inner_product	adjacent_difference partial_sum
C library
qsort	bsearch

 

Defined in header <algorithm>
template< class InputIt, class OutputIt > OutputIt unique_copy( InputIt first, InputIt last,                       OutputIt d_first );	(1)
template< class InputIt, class OutputIt, class BinaryPredicate > OutputIt unique_copy( InputIt first, InputIt last,                       OutputIt d_first, BinaryPredicate p );	(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.

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:  bool pred(const Type1 &a, const Type2 &b); The signature does not need to have const &, but the function must not modify the objects passed to it. The types Type1 and Type2 must be such that an object of type InputIt can be dereferenced and then implicitly converted to both of them. ​
Type requirements
- InputIt must meet the requirements of InputIterator.
- OutputIt must meet the requirements of OutputIterator.
- The type of dereferenced InputIt must meet the requirements of CopyAssignable. if InputIt does not satisfy ForwardIterator
- The type of dereferenced InputIt must meet the requirements of CopyConstructible. if neither InputIt nor OutputIt satisfies ForwardIterator, or if InputIt does not satisfy ForwardIterator and the value type of InputIt differs from that of OutputIt

Return value

Output iterator to the element past the last written element

Complexity

For nonempty ranges, exactly std::distance(first, last) - 1 applications of the corresponding comparator.

Notes

If InputIt satisfies ForwardIterator, this function rereads the input in order to detect duplicates.

Otherwise, if OutputIt satisfies ForwardIterator, and the value type of InputIt is the same as that of OutputIt, this function compare *d_first to *first.

Otherwise, this function compares *first to a local element copy.

Example

Run this code

#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!

See also

adjacent_find	finds the first two adjacent items that are equal (or satisfy a given predicate) (function template)
unique	removes consecutive duplicate elements in a range (function template)
std::experimental::parallel::unique_copy (parallelism TS)	parallelized version of std::unique_copy (function template)