# Problem Definition

## Description

All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: "ACGAATTCCG". When studying DNA, it is sometimes useful to identify repeated sequences within the DNA.

Write a function to find all the 10-letter-long sequences (substrings) that occur more than once in a DNA molecule.

**Example:**

```plaintext
Input: s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT"

Output: ["AAAAACCCCC", "CCCCCAAAAA"]
```

## Notes

1. [LeetCode discussion - 7 lines simple Java, O(n)](https://leetcode.com/problems/repeated-dna-sequences/discuss/53855/7-lines-simple-Java-O(n))
1. [LeetCode discussion - Clean Java solution (hashmap + bits manipulation)](https://leetcode.com/problems/repeated-dna-sequences/discuss/53867/Clean-Java-solution-(hashmap-+-bits-manipulation))