Question

For example: int A[] = {3,2,1,2,3,2,1,3,1,2,3};

How to sort this array efficiently?

This is for a job interview, I need just a pseudo-code.

Answer 1

Problem description: You have n buckets, each bucket contain one coin , the value of the coin can be 5 or 10 or 20. you have to sort the buckets under this limitation: 1. you can use this 2 functions only: SwitchBaskets (Basket1, Basket2) – switch 2 baskets GetCoinValue (Basket1) – return Coin Value in selected basket 2. you cant define array of size n 3. use the switch function as little as possible.

My simple pseudo-code solution, which can be implemented in any language with O(n) complexity.

I will pick coin from basket
1) if it is 5 – push it to be the first,
2)if it is 20- push it to be the last,
3)If 10 – leave it where it is.
4) and look at the next bucket in line.

Edit: if you can’t push elements to the first or last position then Merge sort would be ideally for piratical implementation. Here is how it will work:

Merge sort takes advantage of the ease of merging already sorted lists into a new sorted list. It starts by comparing every two elements (i.e., 1 with 2, then 3 with 4…) and swapping them if the first should come after the second. It then merges each of the resulting lists of two into lists of four, then merges those lists of four, and so on; until at last two lists are merged into the final sorted list. Of the algorithms described here, this is the first that scales well to very large lists, because its worst-case running time is O(n log n). Merge sort has seen a relatively recent surge in popularity for practical implementations, being used for the standard sort routine in the programming languages