reference binding to null pointer of type 'std::vector<int, std::allocator<int>>' (stl_vector.h)

This error occurs when you try to reference a null pointer of type 'std::vector<int, std::allocator<int>>'. It means that you have a vector object that has not been properly initialized or has been deleted, and you are trying to access its elements.

To fix this error, you need to make sure that the vector object is properly initialized and not deleted before you access its elements. You can also check if the pointer is null before accessing its elements to avoid this error.

For example, the following code will result in the error:

std::vector<int> *v = nullptr;
int x = (*v)[0]; // error: reference binding to null pointer of type 'std::vector<int, std::allocator<int>>'

To fix this error, you need to initialize the vector object before accessing its elements:

std::vector<int> v = {1, 2, 3};
int x = v[0]; // no error

Or check if the pointer is null before accessing the elements:

std::vector<int> *v = nullptr;
if (v != nullptr) {
    int x = (*v)[0]; // no error
}