Ruby

1# @param {Character[]} s
2# @return {Void} Do not return anything, modify s in-place instead.
3def reverse_string(s)
4  size = s.size
5  half = size/2
6  for i in 0...half do
7    s[i], s[size-i-1] = [s[size-i-1], s[i]] 
8  end
9  s
10end