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      std::remove_copy,std::remove_copy_if

      From cppreference.com
      <cpp‎ |algorithm
       
       
      Algorithm library
      Constrained algorithms and algorithms on ranges(C++20)
      Constrained algorithms, e.g.ranges::copy,ranges::sort, ...
      Execution policies(C++17)
      Sorting and related operations
      Partitioning operations
      Sorting operations
      Binary search operations
      (on partitioned ranges)
      Set operations (on sorted ranges)
      Merge operations (on sorted ranges)
      Heap operations
      Minimum/maximum operations
      (C++11)
      (C++17)
      Lexicographical comparison operations
      Permutation operations
      C library
      Numeric operations
      Operations on uninitialized memory
       
      Defined in header<algorithm>
      (1)
      template<class InputIt,class OutputIt,class T>

      OutputIt remove_copy( InputIt first, InputIt last,

                            OutputIt d_first,const T& value);
      (constexpr since C++20)
      (until C++26)
      template<class InputIt,class OutputIt,

               class T=typenamestd::iterator_traits
                             <InputIt>::value_type>
      constexpr OutputIt remove_copy( InputIt first, InputIt last,

                                      OutputIt d_first,const T& value);
      (since C++26)
      (2)
      template<class ExecutionPolicy,

               class ForwardIt1,class ForwardIt2,class T>
      ForwardIt2 remove_copy( ExecutionPolicy&& policy,
                              ForwardIt1 first, ForwardIt1 last,

                              ForwardIt2 d_first,const T& value);
      (since C++17)
      (until C++26)
      template<class ExecutionPolicy,

               class ForwardIt1,class ForwardIt2,
               class T=typenamestd::iterator_traits
                             <ForwardIt1>::value_type>
      ForwardIt2 remove_copy( ExecutionPolicy&& policy,
                              ForwardIt1 first, ForwardIt1 last,

                              ForwardIt2 d_first,const T& value);
      (since C++26)
      template<class InputIt,class OutputIt,class UnaryPred>

      OutputIt remove_copy_if( InputIt first, InputIt last,

                               OutputIt d_first, UnaryPred p);
      (3)(constexpr since C++20)
      template<class ExecutionPolicy,

               class ForwardIt1,class ForwardIt2,class UnaryPred>
      ForwardIt2 remove_copy_if( ExecutionPolicy&& policy,
                                 ForwardIt1 first, ForwardIt1 last,

                                 ForwardIt2 d_first, UnaryPred p);
      (4)(since C++17)

      Copies elements from the range[firstlast), to another range beginning atd_first, omitting the elements which satisfy specific criteria.

      1) Ignores all elements that are equal tovalue (usingoperator==).
      3) Ignores all elements for which predicatep returnstrue.
      2,4) Same as(1,3), but executed according topolicy.
      These overloads participate in overload resolution only if all following conditions are satisfied:

      std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> istrue.

      (until C++20)

      std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> istrue.

      (since C++20)

      If*d_first=*first is invalid(until C++20)*first is notwritable tod_first(since C++20), the program is ill-formed.

      If source and destination ranges overlap, the behavior is undefined.

      Contents

      [edit]Parameters

      first, last - the pair of iterators defining the sourcerange of elements to copy
      d_first - the beginning of the destination range
      value - the value of the elements not to copy
      policy - theexecution policy to use
      Type requirements
      -
      InputIt must meet the requirements ofLegacyInputIterator.
      -
      OutputIt must meet the requirements ofLegacyOutputIterator.
      -
      ForwardIt1, ForwardIt2 must meet the requirements ofLegacyForwardIterator.
      -
      UnaryPred must meet the requirements ofPredicate.

      [edit]Return value

      Iterator to the element past the last element copied.

      [edit]Complexity

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

      1,2) Exactly\(\scriptsize N\)N comparisons withvalue usingoperator==.
      3,4) Exactly\(\scriptsize N\)N applications of the predicatep.

      For the overloads with an ExecutionPolicy, there may be a performance cost ifForwardIt1'svalue_type is notMoveConstructible.

      [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

      remove_copy (1)
      template<class InputIt,class OutputIt,class T=typenamestd::iterator_traits<InputIt>::value_type>constexpr 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;}
      remove_copy_if (3)
      template<class InputIt,class OutputIt,class UnaryPred>constexpr OutputIt remove_copy_if(InputIt first, InputIt last,                                  OutputIt d_first, UnaryPred p){for(; first!= last;++first)if(!p(*first))*d_first++=*first;return d_first;}

      [edit]Notes

      Feature-test macroValueStdFeature
      __cpp_lib_algorithm_default_value_type202403(C++26)List-initialization for algorithms(1,2)

      [edit]Example

      Run this code
      #include <algorithm>#include <complex>#include <iomanip>#include <iostream>#include <iterator>#include <string>#include <vector> int main(){// Erase the hash characters '#' on the fly.std::string str="#Return #Value #Optimization";std::cout<<"before: "<<std::quoted(str)<<'\n'; std::cout<<"after:\"";    std::remove_copy(str.begin(), str.end(),std::ostream_iterator<char>(std::cout),'#');std::cout<<"\"\n"; // Erase {1, 3} value on the fly.std::vector<std::complex<double>> nums{{2,2},{1,3},{4,8},{1,3}};    std::remove_copy(nums.begin(), nums.end(),std::ostream_iterator<std::complex<double>>(std::cout),#ifdef __cpp_lib_algorithm_default_value_type{1,3});// T gets deduced#elsestd::complex<double>{1,3});#endif}

      Output:

      before: "#Return #Value #Optimization"after:  "Return Value Optimization"(2,2)(4,8)

      [edit]Defect reports

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

      DRApplied toBehavior as publishedCorrect behavior
      LWG 779C++98T was required to beEqualityComparable, but
      the value type ofForwardIt is not alwaysT
      required*d_first=*first
      to be valid instead

      [edit]See also

      removes elements satisfying specific criteria
      (function template)[edit]
      copies a range of elements to a new location
      (function template)[edit]
      copies a range dividing the elements into two groups
      (function template)[edit]
      copies a range of elements omitting those that satisfy specific criteria
      (algorithm function object)[edit]
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/algorithm/remove_copy&oldid=180585"

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