Sorting Mail

You are given a list of strings mailboxes. Each mailbox is a list of strings, where each string is either "junk", "personal", "work". Go through each mailbox in round robin order starting from the first one, filtering out junk, to form a single pile and return the pile.

Constraints

• 0 ≤ n ≤ 100,000 where n is the number of elements in mailboxes

https://binarysearch.com/problems/Sorting-Mail

Examples

Example 1

Input

• mailboxes = [['work', 'personal'], ['junk', 'personal', 'junk'], ['work']]

Output

• answer = ['work', 'work', 'personal', 'personal']

Explanation

In order and without filtering, we’d have work -> junk -> work -> personal -> personal -> junk, and since we filter out junk we get work -> work -> personal -> personal.

Solution