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Tested Python solution for LeetCode 247 with 14 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 247 # by problem number
lcpy gen -s strobogrammatic_number_ii # by problem name
n, return all the strobogrammatic numbers that are of length n. You may return the answer in any order.
A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).
Input: n = 2
Output: ["11","69","88","96"]
Input: n = 1
Output: ["0","1","8"]
1 <= n <= 14class Solution:
# Time: O(2^n)
# Space: O(2^n)
def find_strobogrammatic(self, n: int) -> list[str]:
def build(length: int) -> list[str]:
if length == 0:
return [""]
if length == 1:
return ["0", "1", "8"]
results: list[str] = []
for middle in build(length - 2):
for left, right in ("11", "88", "69", "96"):
results.append(left + middle + right)
if length != n:
results.append("0" + middle + "0")
return results
return build(n)
| Time | Space |
|---|---|
| O(2^n) | O(2^n) |