Looking for an algorithm to spit out a sequence of numbers in a (pseudo) random order

Question

Suppose I have a sequence of numbers: {n, n+1, n+2, ... n + m}

Without storing the numbers ahead of time I want to create a function f(), which given the sequence {1,2,3

Answer 1

This question is analogous to shuffling a deck of (m + 1) cards, numbered [n, ..., n + m]. Notice that the numbering (and thus n) is unimportant; what matters is that we can tell the cards apart. (You can simply add the n back later if desired.)

To do what you want, you can perform a Fisher-Yates shuffle and just keep track of which indices have been selected for shuffling so far. This will allow you to avoid storing another copy of the values themselves, as requested.