To initialize a std::vector class template, you can use any of the following methods, but you are not restricted to only these:

• Initialize from an initialization list:

        std::vector<int> v1 { 1, 2, 3, 4, 5 };

• Initialize from a C-like array:

        int arr[] = { 1, 2, 3, 4, 5 }; 
        std::vector<int> v2(arr, arr + 5); // { 1, 2, 3, 4, 5 }

• Initialize from another container:

        std::list<int> l{ 1, 2, 3, 4, 5 }; 
        std::vector<int> v3(l.begin(), l.end()); //{ 1, 2, 3, 4, 5 }

• Initialize from a count and a value:

        std::vector<int> v4(5, 1); // {1, 1, 1, 1, 1}

To modify the content of std::vector, use any of the following methods, but you are not restricted to only these:

• Add an element at the end of the vector with push_back():

        std::vector<int> v1{ 1, 2, 3, 4, 5 };
        v1.push_back(6); // v1 = { 1, 2, 3, 4, 5, 6 }

• Remove an element from the end of the vector with pop_back():

        v1.pop_back();

• Insert anywhere in the vector with insert():

        int arr[] = { 1, 2, 3, 4, 5 };
        std::vector<int> v2;
        v2.insert(v2.begin(), arr, arr + 5); // v2 = { 1, 2, 3, 4, 5 }

• Add an element by creating it at the end of the vector with emplace_back():

        struct foo
        {
          int a;
          double b;
          std::string c;

          foo(int a, double b, std::string const & c) :
            a(a), b(b), c(c) {}
        };

        std::vector<foo> v3;
        v3.emplace_back(1, 1.0, "one"s); 
        // v3 = { foo{1, 1.0, "one"} }

• Insert an element by creating it anywhere in the vector with emplace():

        v3.emplace(v3.begin(), 2, 2.0, "two"s);
        // v3 = { foo{2, 2.0, "two"}, foo{1, 1.0, "one"} }

To modify the whole content of the vector, use any of the following methods, but you are not restricted to only these:

• Assign from another vector with operator=; this replaces the content of the container:

        std::vector<int> v1{ 1, 2, 3, 4, 5 };
        std::vector<int> v2{ 10, 20, 30 };
        v2 = v1; // v1 = { 1, 2, 3, 4, 5 }

• Assign from another sequence defined by a begin and end iterator with the assign() method; this replaces the content of the container:

        int arr[] = { 1, 2, 3, 4, 5 };
        std::vector<int> v3;
        v3.assign(arr, arr + 5); // v3 = { 1, 2, 3, 4, 5 }

• Swap the content of two vectors with the swap() method:

        std::vector<int> v4{ 1, 2, 3, 4, 5 };
        std::vector<int> v5{ 10, 20, 30 };
        v4.swap(v5); // v4 = { 10, 20, 30 }, v5 = { 1, 2, 3, 4, 5 }

• Remove all the elements with the clear() method:

        std::vector<int> v6{ 1, 2, 3, 4, 5 };
        v6.clear(); // v6 = { }

• Remove one or more elements with the erase() method (which requires either an iterator or a pair of iterators that define the range of elements from the vector to be removed):

        std::vector<int> v7{ 1, 2, 3, 4, 5 };
        v7.erase(v7.begin() + 2, v7.begin() + 4); // v7 = { 1, 2, 5 }

To get the address of the first element in a vector, usually to pass the content of a vector to a C-like API, use any of the following methods:

• Use the data() method, which returns a pointer to the first element, providing direct access to the underlying contiguous sequence of memory where the vector elements are stored; this is only available since C++11:

        void process(int const * const arr, int const size) 
        { /* do something */ }

        std::vector<int> v{ 1, 2, 3, 4, 5 };
        process(v.data(), static_cast<int>(v.size()));

• Get the address of the first element:

        process(&v[0], static_cast<int>(v.size()));

• Get the address of the element referred by the front() method:

        process(&v.front(), static_cast<int>(v.size()));

• Get the address of the element pointed by the iterator returned from begin():

        process(&*v.begin(), static_cast<int>(v.size()));