Combining two lists in C++ - c++

Question

If I had two lists A and B, how can I add all the elements of B to the beginning of list A, without "emptying" the B list. I basically want to just transfer copies of B list into the beginning of A list. I'm thinking about using insert and want to double check on the syntax.
I know if I was adding it to the end it would be:
A.insert(A.end(), B.begin(), B.end());
so to insert it at the beginning would it be:
A.insert(A.begin(), B.begin(), B.end());
??

Answer 1

That can be achieved with one line, using the fact a list can be iterated both ways.
copy(A.rbegin(), A.rend(), front_inserter(B));
Complete example (C++11 for list constructors and printing code, but answer is C++03 valid):
#include <list>
#include <iterator>
#include <algorithm>
#include <iostream>
int main() {
// Create lists
std::list<char> A = {'a','b'};
std::list<char> B = {'c','d'};
// Insert A at the beginning of B
copy(A.rbegin(), A.rend(), front_inserter(B));
// Print result
for(auto c : B)
std::cout << c;
std::cout << "\n";
return 0;
}

Answer 2

Make a temporary copy of the list you want to append without emptying, then splice the temporary list into the original. Here is and example.
#include <iostream>
#include <list>
#include <vector>
int main ()
{
std::list<int> mylist;
std::list<int>::iterator it;
std::list<int> otherList;
std::list<int> combinedList;
// set some initial values:
for (int i=1; i<=5; ++i) mylist.push_back(i); // 1 2 3 4 5
for (int i=6; i<=10; i++) otherList.push_back(i); // 6 7 8 9 10
std::list<int> temp = otherList;
combinedList = mylist;
it = combinedList.begin();
combinedList.splice(it, temp);
std::cout << "mylist contains:";
for (it=combinedList.begin(); it!=combinedList.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
std::cout<<"orignal appended list:"<<std::endl;
for(it=otherList.begin(); it!=otherList.end(); ++it)
std::cout<<' '<<*it;
std::cout<<'\n';
return 0;
}
http://ideone.com/e.js/Ol6Wk1