Leetcode 1593. Split a String Into the Max Number of Unique Substrings

Seawolf

Given a string s, return the maximum number of unique substrings that the given string can be split into.

You can split string s into any list of non-empty substrings, where the concatenation of the substrings forms the original string. However, you must split the substrings such that all of them are unique.

A substring is a contiguous sequence of characters within a string.



Example 1:

Input: s = "ababccc"
Output: 5
Explanation: 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.
Example 2:

Input: s = "aba"
Output: 2
Explanation: One way to split maximally is ['a', 'ba'].
Example 3:

Input: s = "aa"
Output: 1
Explanation: It is impossible to split the string any further.


Constraints:

1 <= s.length <= 16

s contains only lower case English letters.

class Solution:
    def maxUniqueSplit(self, s: str) -> int:
        def backtrack(s, hashset):
            max_val = 0
            
            for i in range(1, len(s) + 1):
                curt = s[:i]
                
                if curt not in hashset:
                    hashset.add(curt)
                    max_val = max(max_val, 1 + backtrack(s[i:], hashset))
                    hashset.discard(curt)
            
            return max_val
        
        return backtrack(s, set())