For this problem I would write something like this: Input: array of unique characters Output: either an empty string if I can't find it or the smallest substring containing the characters in my array. I like to start any algorithm problem by making sure I understand the question and then writing out what my expected inputs and outputs are as well as any notes I want to remember about those values. Return an empty string if a substring containing these characters does not exist. Here is our question: Given an array of unique characters called array and a string called string, Write a function that finds the smallest substring of string containing all the characters in array. Today we are going to look for the smallest substring that has the elements of a given array. There are a ton of variations of problems where this technique is useful. Usually during this process you keep track of what you found, that might be the length of a substring, it might be characters in a substring. When when it is no longer doing its job you make the window smaller again by moving the starting point until it starts doing what you want it to again.

As long as it is still looking for what you need it to look for keep moving the ending point. The basic idea behind this approach is to make a starting point and an ending point for your window and then make the window bigger by moving the ending point.

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