Sinusoidal string

1class Solution:
2    def sinusoidalString(self, s):
3        res = []
4        # peaks: loop through s from 1 to len(s) in increments of 4 and append to res
5        # middle: loop through s from 0 to len(s) in increments of 2
6        # troughs: loop through s from 3 to len(s) in increments of 4 and append to res
7        i = 1
8        while i < len(s):
9            res.append(s[i])
10            i += 4
11        
12        i = 0
13        while i < len(s):
14            res.append(s[i])
15            i += 2
16        
17        i = 3
18        while i < len(s):
19            res.append(s[i])
20            i += 4
21
22        return "".join(res)