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Tested Python solution for LeetCode 1593 with 18 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 1593 # by problem number
lcpy gen -s split_a_string_into_the_max_number_of_unique_substrings # by problem name
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.
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.
Input: s = "aba"
Output: 2
Explanation: One way to split maximally is ['a', 'ba'].
Input: s = "aa"
Output: 1
Explanation: It is impossible to split the string any further.
1 <= s.length <= 16s contains only lower case English letters.class Solution:
# Time: O(n * 2^n) worst case, pruned hard by the remaining-suffix bound
# Space: O(n) recursion depth plus the seen-set of at most n pieces
def max_unique_split(self, s: str) -> int:
n = len(s)
seen: set[str] = set()
def dfs(start: int, count: int) -> int:
best = count
for end in range(start + 1, n + 1):
piece = s[start:end]
# Even taking every remaining character as its own split cannot
# beat the best found so far.
if piece in seen or count + 1 + (n - end) <= best:
continue
seen.add(piece)
best = max(best, dfs(end, count + 1))
seen.remove(piece)
return best
return dfs(0, 0)
| Time | Space |
|---|---|
| O(n * 2^n) worst case, pruned hard by the remaining-suffix bound | O(n) recursion depth plus the seen-set of at most n pieces |