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Tested Python solution for LeetCode 541 with 18 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 541 # by problem number
lcpy gen -s reverse_string_ii # by problem name
s and an integer k, reverse the first k characters for every 2k characters counting from the start of the string.
If there are fewer than k characters left, reverse all of them. If there are less than 2k but greater than or equal to k characters, then reverse the first k characters and leave the other as original.
Input: s = "abcdefg", k = 2
Output: "bacdfeg"
Input: s = "abcd", k = 2
Output: "bacd"
class Solution:
# Time: O(n)
# Space: O(n)
def reverse_str(self, s: str, k: int) -> str:
chars = list(s)
for i in range(0, len(chars), 2 * k):
chars[i : i + k] = reversed(chars[i : i + k])
return "".join(chars)
| Time | Space |
|---|---|
| O(n) | O(n) |