# Returning random integer from interval based on last result and a seed Suppose we have an interval of integers [a, b]. I would like to have a function that returns random members from within the interval, without repetitions. Once that all members within the interval are explored, the function would start to return the same first random sequence again, in the same order.

Example: a=1, b=5

``3, 1, 4, 5, 2, 3, 1, 4, 5, 2, 3, 1, 4, 5, 2, ... ``

This would be easy to achieve by shuffling an array of all elements between a and b, and repeating it once the array is finished. However, this would take too much memory space, and this is not suitable for my case (I might have millions of elements).

Instead, the function I’d like to have would be more or less like this:

``f(a, b, n, seed) -> n+1 ``

Where:

``a - start of interval b - end of interval n - last element returned from list seed - self-explanatory n+1 - next random element from list, calculated by using the seed and the last element returned (n) ``

The trick is knowing some way to get a non-repeated number from the interval based only on the element returned before and the seed. In the end, it would behave like a circular list randomized at its initialization, but without using memory space. Posted on Categories proxies