<p>Given a string <code>s</code><var>,</var> return <em>the maximum number of unique substrings that the given string can be split into</em>.</p>
<p>You can split string <code>s</code> into any list of <strong>non-empty substrings</strong>, where the concatenation of the substrings forms the original string. However, you must split the substrings such that all of them are <strong>unique</strong>.</p>
<p>A <strong>substring</strong> is a contiguous sequence of characters within a string.</p>
<strong>Explanation</strong>: One way to split maximally is ['a', 'b', 'ab', 'c', 'cc']. Splitting like ['a', 'b', 'a', 'b', 'c', 'cc'] is not valid as you have 'a' and 'b' multiple times.
