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

Problem Link

Description

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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.

Solution

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Python3

class Solution:
    def maxUniqueSplit(self, s: str) -> int:
        N = len(s)
        used = set()
        res = -inf
 
        def backtrack(index, curr, count):
            if index == N:
                nonlocal res
                res = max(res, count)
                return
 
            add = curr + s[index]
            if add not in used:
                used.add(add)
                backtrack(index + 1, "", count + 1)
                used.remove(add)
            
            backtrack(index + 1, add, count)
        
        backtrack(0, "", 0)
 
        return res