Reorder a String by Alternating Its Front and Back Characters

Given a string s, build a new string by taking characters alternately from the front and the back of s: the first character, then the last character, then the second character, then the second-to-last character, and so on, until every character of s has been used exactly once.

Function Signature

def reorder_front_back(s: str) -> str:

Rules

• Let n = len(s). The output is s[0], s[n-1], s[1], s[n-2], s[2], s[n-3], and so on, stopping as soon as n characters have been written.
• Every position of s is used exactly once, so the output also has length n. When n is odd, the middle character s[n // 2] is the last one written.
• Characters are copied unchanged.

Constraints

• 1 <= len(s) <= 10^5
• s consists of lowercase English letters.

Examples

Example 1

Input: s = "abcdef"
Output: "afbecd"

The characters are taken in the order a (first), f (last), b (second), e (second-to-last), c, d.

Example 2

Input: s = "hello"
Output: "hoell"

The order is h (first), o (last), e (second), l (second-to-last), and finally the middle l.

Example 3

Input: s = "x"
Output: "x"