Binary Search

Instructions

Your task is to implement a binary search algorithm.

A binary search algorithm finds an item in a list by repeatedly splitting it in half, only keeping the half which contains the item we're looking for. It allows us to quickly narrow down the possible locations of our item until we find it, or until we've eliminated all possible locations.

The algorithm looks like this:

• Find the middle element of a sorted list and compare it with the item we're looking for.
• If the middle element is our item, then we're done!
• If the middle element is greater than our item, we can eliminate that element and all the elements after it.
• If the middle element is less than our item, we can eliminate that element and all the elements before it.
• If every element of the list has been eliminated then the item is not in the list.
• Otherwise, repeat the process on the part of the list that has not been eliminated.

Here's an example:

Let's say we're looking for the number 23 in the following sorted list: [4, 8, 12, 16, 23, 28, 32].

• We start by comparing 23 with the middle element, 16.
• Since 23 is greater than 16, we can eliminate the left half of the list, leaving us with [23, 28, 32].
• We then compare 23 with the new middle element, 28.
• Since 23 is less than 28, we can eliminate the right half of the list: [23].
• We've found our item.

Restrictions

Rust provides in its standard library already a binary search function. For this exercise you should not use this function but just other basic tools instead.

For bonus points

Did you get the tests passing and the code clean? If you want to, there are some additional things you could try.

• Currently your find function will probably only work for slices of numbers, but the Rust type system is flexible enough to create a find function which works on all slices which contains elements which can be ordered.
• Additionally this find function can work not only on slices, but at the same time also on a Vec or an Array.

To run the bonus tests, remove the #[ignore] flag and execute the tests with the generic feature, like this:

$ cargo test --features generic

Then please share your thoughts in a comment on the submission. Did this experiment make the code better? Worse? Did you learn anything from it?

---

Source

Wikipedia