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541. Reverse String II

Two Pointers String

Problem - Reverse String II

Easy

Given a string 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.

 

Example 1:

Input: s = "abcdefg", k = 2
Output: "bacdfeg"

Example 2:

Input: s = "abcd", k = 2
Output: "bacd"

 

Constraints:

  • 1 <= s.length <= 104
  • s consists of only lowercase English letters.
  • 1 <= k <= 104

Solutions

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class Solution:
    def reverseStr(self, s: str, k: int) -> str:
        chars = list(s)
        for i in range(0, len(s), k * 2):
            chars[i : i + k] = reversed(s[i : i + k])
        return "".join(chars)

Submission Stats:

  • Runtime: 0 ms (100.00%)
  • Memory: 18.1 MB (8.01%)