std::remove, std::remove_if

 

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all_of any_of none_of (C++11) (C++11) (C++11) for_each count count_if mismatch equal	find find_if find_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copy copy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n remove remove_if remove_copy remove_copy_if	replace replace_if replace_copy replace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffle shuffle   (C++11) unique unique_copy
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is_partitioned (C++11) partition partition_copy (C++11)	stable_partition partition_point (C++11)
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is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
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lower_bound upper_bound	binary_search equal_range
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max max_element min min_element minmax (C++11) minmax_element (C++11)	lexicographical_compare is_permutation (C++11) next_permutation prev_permutation
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iota (C++11) accumulate inner_product	adjacent_difference partial_sum
C library
qsort	bsearch

 

Defined in header <algorithm>
template< class ForwardIt, class T > ForwardIt remove( ForwardIt first, ForwardIt last, const T& value );	(1)
template< class ForwardIt, class UnaryPredicate > ForwardIt remove_if( ForwardIt first, ForwardIt last, UnaryPredicate p );	(2)

Removes all elements satisfying specific criteria from the range [first, last). The first version removes all elements that are equal to value, the second version removes all elements for which predicate p returns true.

Removing is done by shifting the elements in the range in such a way that elements to be erased are overwritten. Relative order of the elements that remain is preserved. Iterators pointing to an elements between the old and the new ends of the range are still dereferenceable, but the elements themselves have unspecified values. The function returns an iterator to the new end of the range.

Parameters

first, last	-	the range of elements to process
value	-	the value of elements to remove
p	-	unary predicate which returns ​true if the element should be removed. 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. The type Type must be such that an object of type ForwardIt can be dereferenced and then implicitly converted to Type. ​
Type requirements
- ForwardIt must meet the requirements of ForwardIterator.
- The type of dereferenced ForwardIt must meet the requirements of MoveAssignable.
- UnaryPredicate must meet the requirements of Predicate.

Return value

Iterator to the new end of the range

Complexity

Exactly std::distance(first, last) applications of the predicate.

Notes

The similarly-named container member functions list::remove, list::remove_if, forward_list::remove, and forward_list::remove_if erase the removed elements.

Possible implementation

First version
template<class ForwardIt, class T> ForwardIt remove(ForwardIt first, ForwardIt last, const T& value) { ForwardIt result = first; for (; first != last; ++first) { if (!(*first == value)) { *result++ = *first; } } return result; }
Second version
template<class ForwardIt, class UnaryPredicate> ForwardIt remove_if(ForwardIt first, ForwardIt last, UnaryPredicate p) { ForwardIt result = first; for (; first != last; ++first) { if (!p(*first)) { *result++ = *first; } } return result; }

Examples

The following code removes all spaces from a string by shifting all non-space characters to the left and then erasing the extra. This is an example of erase-remove idiom.

run this code

#include <algorithm>
#include <string>
#include <iostream>
#include <ctype.h>
int main()
{
    std::string str1 = "Text with some   spaces";
    str1.erase(std::remove(str1.begin(), str1.end(), ' '),
              str1.end());
    std::cout << str1 << '\n';
 
    std::string str2 = "Text\n with\tsome \t  whitespaces\n\n";
    str2.erase(std::remove_if(str2.begin(), str2.end(), ::isspace),
               str2.end());
    std::cout << str2 << '\n';
}

Output:

Textwithsomespaces
Textwithsomewhitespaces

See also

remove_copy remove_copy_if	copies a range of elements omitting those that satisfy specific criteria (function template)