Removes all elements satisfying specific criteria from the range[first, last) and returns a past-the-end iterator for the new end of the range.

[edit]Explanation

Removing is done by shifting the elements in the range in such a way that the elements that are not to be removed appear in the beginning of the range.

• Shifting is done bycopy assignment(until C++11)move assignment(since C++11).
• The removing operation is stable: the relative order of the elements not to be removed stays the same.
• The underlying sequence of[first, last) is not shortened by the removing operation. Givenresult as the returned iterator:

• All iterators in[result, last) are stilldereferenceable.

[edit]Parameters

[edit]Return value

Past-the-end iterator for the new range of values (if this is notend, then it points to an unspecified value, and so do iterators to any values between this iterator andend).

[edit]Complexity

Given\(\scriptsize N\)N asstd::distance(first, last):

[edit]Exceptions

The overloads with a template parameter namedExecutionPolicy report errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception andExecutionPolicy is one of thestandard policies,std::terminate is called. For any otherExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory,std::bad_alloc is thrown.

[edit]Possible implementation

template<class ForwardIt,class T=typenamestd::iterator_traits<ForwardIt>::value_type>ForwardIt remove(ForwardIt first, ForwardIt last,const T& value){    first=std::find(first, last, value);if(first!= last)for(ForwardIt i= first;++i!= last;)if(!(*i== value))*first++= std::move(*i);return first;}

template<class ForwardIt,class UnaryPred>ForwardIt remove_if(ForwardIt first, ForwardIt last, UnaryPred p){    first=std::find_if(first, last, p);if(first!= last)for(ForwardIt i= first;++i!= last;)if(!p(*i))*first++= std::move(*i);return first;}

[edit]Notes

A call toremove is typically followed by a call to a container'serase member function to actually remove elements from the container. These two invocations together constitute a so-callederase-remove idiom.

The similarly-named containermember functionslist::remove,list::remove_if,forward_list::remove, andforward_list::remove_if erase the removed elements.

These algorithms cannot be used with associative containers such asstd::set andstd::map because their iterator types do not dereference toMoveAssignable types (the keys in these containers are not modifiable).

The standard library also defines an overload ofstd::remove in<cstdio>, which takes aconstchar* and is used to delete files.

Becausestd::remove takesvalue by reference, it can have unexpected behavior if it is a reference to an element of the range[first, last).

[edit]Example

#include <algorithm>#include <cassert>#include <cctype>#include <complex>#include <iomanip>#include <iostream>#include <string>#include <string_view>#include <vector> int main(){std::string str1{"Quick  Red  Dog"};std::cout<<"1) "<<std::quoted(str1)<<'\n';constauto noSpaceEnd= std::remove(str1.begin(), str1.end(),' ');std::cout<<"2) "<<std::quoted(str1)<<'\n'; // The spaces are removed from the string only logically.// Note, we use view, the original string is still not shrunk:std::cout<<"3) "<<std::quoted(std::string_view(str1.begin(), noSpaceEnd))<<", size: "<< str1.size()<<'\n';     str1.erase(noSpaceEnd, str1.end());// The spaces are removed from the string physically.std::cout<<"4) "<<std::quoted(str1)<<", size: "<< str1.size()<<'\n'; std::string str2="Jumped\n Over\tA\vLazy\t  Fox\r\n";    str2.erase(std::remove_if(str2.begin(),                               str2.end(),[](unsignedchar x){returnstd::isspace(x);}),               str2.end());std::cout<<"5) "<<std::quoted(str2)<<'\n'; std::vector<std::complex<double>> nums{{2,2},{1,3},{4,8}};#ifdef __cpp_lib_algorithm_default_value_type        nums.erase(std::remove(nums.begin(), nums.end(),{1,3}), nums.end());#else        nums.erase(std::remove(nums.begin(), nums.end(),std::complex<double>{1,3}),                   nums.end());#endifassert((nums==std::vector<std::complex<double>>{{2,2},{4,8}}));}

1) "Quick  Red  Dog"2) "QuickRedDog Dog"3) "QuickRedDog", size: 154) "QuickRedDog", size: 115) "JumpedOverALazyFox"

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit]See also

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