insert list to end of vector

Question

Is there an easy way to insert an entire list to the end of a vector without inserting the front value and popping it for the entire list? Right now, I'm doing thing:

std::vector<int> v({1,2,3});
std::list<int> l({5,7,9});
for (int i=0; i<3; i++) {
    v.push_back(l.front());
    l.pop_front();
}

I'm hoping for some way to easily just iterate through the list and insert it into the vector.

Answer 1

You need to insert at the end of v. Both vector and list have iterators so its pretty straight forward.

You can replace your for loop with this single line:

v.insert(v.end(), l.begin(), l.end());

Here is the updated code:

#include <iostream>
#include <vector>
#include <list>

int main() {
    std::cout << "Hello, World!\n";
    std::vector<int> v({1,2,3});
    std::list<int> l({5,7,9});

    v.insert(v.end(), l.begin(), l.end());
    l.clear();

    for (int i : v) {
        std::cout << i << " ";
    }

    std::cout << std::endl;

    return 0;
}

output:

Hello, World!
1 2 3 5 7 9 
Program ended with exit code: 0

Answer 2

While the question illustrated int element types, that might have been a simplification while preparing an example, or other readers might find this Q&A when wanting to move non-copyable elements from the list, or types likes std::string that can often¹ be moved faster than copied. To move elements, use:

v.insert(v.end(),
         std::move_iterator{l.begin()}, std::move_iterator{l.end()});
l.clear();

---

¹ in string's case - when longer than any internal Short-String-Optimisation buffer and therefore using dynamically allocated memory