How to insert a vector into another vector in a specific place so that i will get a big vector of both and that place will be overwritten?

Question

for an exercise i really need to know how to insert one vector into another.

here is an example of what i need:

//let's say i have these 2 vecs: 
vec1 = { 18, 192, 34};
vec2 = { 171, 11, 50, 6};

and i choose the point where to connect them, lets say i choose vec 1 to be in place 2 of vector 2 like so:

result_vec = { 171, vec1, 50, 6};

so what i will actually get when i'm done is:

result_vec = { 171, 18, 192, 34, 50, 6};

for me it will be even better to see two examples, a simple example and another example with smart pointers like shared_ptr or unique_ptr.

Thanks!

Answer 1

It seems you want to substitute one element of one vector for elements of another vector. If so then you can write a function similar to that shown in the demonstrative program.

#include <iostream>
#include <vector>
#include <iterator>

template <typename T>
std::vector<T> & replace( std::vector<T> &v1, 
                          typename std::vector<T>::size_type pos,
                          const std::vector<T> &v2 )
{
    if ( not ( pos < v1.size() ) )
    {
        v1.insert( std::end( v1 ), std::begin( v2 ), std::end( v2 ) );
    }
    else
    {
        v1.insert( v1.erase( std::next( v1.begin(), pos ) ),
                   std::begin( v2 ), std::end( v2 ) );
    }

    return v1;
}                          

int main() 
{
    std::vector<int> v1 = { 171, 11, 50, 6 };
    std::vector<int> v2 = { 18, 192, 34 };

    for ( const auto &item : replace( v1, 1, v2 ) ) std::cout << item << ' ';
    std::cout << '\n';

    return 0;
}

The program output is

171 18 192 34 50 6