LeetCode： Reverse String II
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.
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
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