A DNA sequence consists of a series of nucleotides, each represented by one of the characters 'A', 'C', 'G', or 'T'.

Given a string s representing a DNA sequence, find and return all $10$-letter-long substrings that appear more than once within s. The result may be returned in any order.

Constraints:

• $1 \leq$ s.length $\leq 10^5$

• s[i] is one of 'A', 'C', 'G', or 'T'

The key idea is to use a sliding window of fixed size $10$ to scan ...