Description
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
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