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Tested Python solution for LeetCode 1215 with 21 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 1215 # by problem number
lcpy gen -s stepping_numbers # by problem name
1.
321 is a stepping number while 421 is not.low and high, return a sorted list of all the stepping numbers in the inclusive range [low, high].
Input: low = 0, high = 21
Output: [0,1,2,3,4,5,6,7,8,9,10,12,21]
Input: low = 10, high = 15
Output: [10,12]
0 <= low <= high <= 2 * 10^9from collections import deque
class Solution:
# Time: O(2^log(high)) - at most ~10k stepping numbers below 2 * 10^9
# Space: O(2^log(high)) for the queue
def count_stepping_numbers(self, low: int, high: int) -> list[int]:
ans: list[int] = []
if low == 0:
ans.append(0)
q: deque[int] = deque(range(1, 10))
while q:
v = q.popleft()
if v > high:
break
if v >= low:
ans.append(v)
last = v % 10
if last > 0:
q.append(v * 10 + last - 1)
if last < 9:
q.append(v * 10 + last + 1)
return ans
| Time | Space |
|---|---|
| O(2^log(high)) - at most ~10k stepping numbers below 2 * 10^9 | O(2^log(high)) for the queue |