LeetCode： Reverse String II

Question

Given a string and an integer k, you need to reverse the first k characters for every 2k characters counting from the start of the string. If there are less 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 left the other as original.

Example 1:

Input: s = "abcdefg", k = 2

Output: "bacdfeg"

Solution#1

def reverse_str(s, k)
  i = 0
  length = s.length
  while i < length-1
    s.gsub!(s[i...i+k], s[i...i+k].reverse!)
    i += 2*k
  end
  s
end

Solution#2

def reverse_str(s, k)
  for i in (0 ... s.length).step k*2
  	s[i ... i+k] = s[i ... i+k].reverse
  end
  s
end