Fixed allocation std::vector

You can implement or reuse boost's static_vector; A variable-size array container with fixed capacity.

You can always use a C-style array (same as underlying in std::array) as vectors aren't supposed to be static

int arr[5]; // static array of 5 integers

To have it more useful you can wrap it in a class template to hide the C-style Example:

template<class type, std::size_t capacaty>
class StaticVector {
    private:
        type arr[capacaty];
        std::size_t m_size;
    public:
        StaticVector() : m_size(0) {}

        type at(std::size_t index) {
            if (index >=0 && index < m_size) {
                return arr[index];
            }

            return type();
        }

        void remove(std::size_t index) {
            if (index >=0 && index < m_size) {
                for (std::size_t i=index; i < m_size-1; i++) {
                    arr[i] = arr[i+1];
                }
                m_size--;
            }
        }

        void push_back(type val) {
            if (m_size < capacaty) {
                arr[m_size] = val;
                m_size++;
            }
        }

        std::size_t size() {
            return m_size;
        }
};

Example with it in use: https://onlinegdb.com/BkBgSTlZH