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Tested Python solution for LeetCode 784 with 18 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 784 # by problem number
lcpy gen -s letter_case_permutation # by problem name
s, you can transform every letter individually to be lowercase or uppercase to create another string.
Return a list of all possible strings we could create. Return the output in any order.
Input: s = "a1b2"
Output: ["a1b2","a1B2","A1b2","A1B2"]
Input: s = "3z4"
Output: ["3z4","3Z4"]
1 <= s.length <= 12s consists of lowercase English letters, uppercase English letters, and digits.class Solution:
# Time: O(n * 2^k) where k is the number of letters
# Space: O(n * 2^k) for the output
def letter_case_permutation(self, s: str) -> list[str]:
results: list[str] = [""]
for ch in s:
if ch.isalpha():
results = [prefix + alt for prefix in results for alt in (ch.lower(), ch.upper())]
else:
results = [prefix + ch for prefix in results]
return results
| Time | Space |
|---|---|
| O(n * 2^k) where k is the number of letters | O(n * 2^k) for the output |