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Copying the vector elements into std::array


By : gnad
Date : August 01 2020, 02:00 PM
This might help you I have a vector of elements of type uint8 which I am copying into one std::array. After some operations again I need to copy the elements from std::array to a vector.Please find the code below , You could copy by size of vector.
code :
#include <iostream>
#include <vector>
#include <array>
#include <cstdint>
#include <limits>
#include <algorithm>

int main()
{
    std::array<std::uint32_t, 5> elem_arr ;
    std::vector<std::uint32_t> ele_vec {1,2,3};
    std::copy(ele_vec.begin(),ele_vec.end(),elem_arr.begin());
    std::vector<std::uint32_t> ele_vec_copy { elem_arr.begin() , elem_arr.begin() + ele_vec.size() };

    for(auto ele : ele_vec_copy)
        std::cout << ele << std::endl;

    return 0;
}
#include <iostream>
#include <vector>
#include <array>
#include <cstdint>
#include <limits>
#include <algorithm>
#include <limits>

std::array<std::uint32_t, 5> elem_arr;

void copy_from_vector(std::vector<std::uint32_t> elem_vec)
{
    std::copy(elem_vec.begin(),elem_vec.end(),elem_arr.begin());
}

std::vector<std::uint32_t> copy_from_array()
{
    std::vector<std::uint32_t> ele_vec_copy;
    std::copy_if( elem_arr.begin() , elem_arr.end() , 
                  std::back_inserter( ele_vec_copy ) , 
                  []( std::uint32_t val ) { 
                      return val != std::numeric_limits<std::uint32_t>::max(); 

                  } );
    return ele_vec_copy;
}

int main()
{

    elem_arr.fill( std::numeric_limits<std::uint32_t>::max() );
    std::vector<std::uint32_t> ele_vec {1,2,3};

    copy_from_vector(ele_vec);

    auto ele_vec_copy = copy_from_array();

    for(auto ele : ele_vec_copy)
        std::cout << ele << std::endl;

    return 0;
}
#include <iostream>
#include <vector>
#include <array>
#include <cstdint>
#include <limits>
#include <algorithm>
#include <limits>
#include <optional>

std::array<std::optional<std::uint32_t>, 5> elem_arr;

void copy_from_vector(std::vector<std::uint32_t> elem_vec)
{
    std::transform( elem_vec.begin() , elem_vec.end() , 
                    elem_arr.begin() ,
                    []( auto val ) { return std::optional<std::uint32_t>{ val }; }
                   );
}

std::vector<std::uint32_t> copy_from_array()
{
    std::vector<std::uint32_t> ele_vec_copy;
    std::vector<std::optional<std::uint32_t>> non_null_elements;
    std::copy_if( elem_arr.begin() , elem_arr.end() , 
                  std::back_inserter( non_null_elements ) , 
                  []( auto val ) { 
                      return val;
                  } );
    std::transform( non_null_elements.begin(), non_null_elements.end() , 
                    std::back_inserter( ele_vec_copy ) ,
                    []( auto val ) { return *val; } 
                  );
    return ele_vec_copy;
}

int main()
{
    std::vector<std::uint32_t> ele_vec {1,2,3};

    copy_from_vector(ele_vec);

    auto ele_vec_copy = copy_from_array();

    for(auto ele : ele_vec_copy)
        std::cout << ele << std::endl;

    return 0;
}


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Copying elements from a char vector to a string vector


By : alexflores2323
Date : March 29 2020, 07:55 AM
help you fix your problem You had to make sure that your other vector has enough elements in it.
(UPDATE: using postfix operation for v2 will save memory and running time, because in that case no temporary variable has to be allocated to perform the addition operation.)
code :
vector <string> v2(v1.size());
for(int i=0;i<=v1.size();i++){    //v1 is the char vector
    for (int j=0;j<=k;j++){
        v2[i]+=v1[j];
    }
cout<<v2[i]<<endl;
}

Shifting and Copying std::vector elements


By : Capreolus
Date : March 29 2020, 07:55 AM
it fixes the issue Looks like you forgot the template argument for std::vector. Anyway, try something like:
code :
std::vector<int> array2(n+1);
std::vector<int> array1(array2.begin()+1, array2.end());

Copying the elements of one vector into another


By : no name
Date : March 29 2020, 07:55 AM
Any of those help I need to copy the elements of one vector into another, but in the same process I need to be able to remove the comments or garbage from the data. For example; two of the elements are , Say
code :
string str = "(* Month: 2005 01 *) 31";
size_t p = str.find_last_of(" ");
string sub_str = str.substr(p+1)

Copying vector elements to a vector pair


By : MDMC
Date : March 29 2020, 07:55 AM
To fix the issue you can do You have clarified that the arrays will always be of equal size. That's a prerequisite condition.
So, your situation is as follows. You have vector A over here, and vector B over there. You have no guarantees whether the actual memory that vector A uses and the actual memory that vector B uses are next to each other. They could be anywhere.
code :
pairVector.reserve(pairVector.size()+strVector.size());
for (int i = 0; i < strVector.size(); ++i )
    pairVector.push_back(pair<string, int> (strVector[i], intVector[i]));
    pairVector.emplace_back(strVector[i], intVector[i]);
int i=strVector.size();
for (int i = 0; i < n; ++i )

Copying elements of rapidjson::Value to std::vector


By : Achilleas Mantzios
Date : March 29 2020, 07:55 AM
hop of those help? The std::vector vector must be assignable, so you cannot have a std::vector of const references. Instead, try storing either rapidjson::Values or pointers to them. If you really want to store references, check out std::reference_wrapper.
From section 23.2.4 Class template vector of the C++ standard:
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