Sort 1 billion floats in c++

so i was asked this question on an interview. I had to make an algorithm which will sort 1 billion floats. I thought about doing it straightforward by making an array and quicksorting it but it turns out you can't make an array that will take up more than 2bil. bytes.
Yes I am kinda new to c++, but still.
PS in the task it was said that i can use c++14 so maybe there is something that can help?