0187 - Repeated DNA Subsequences

0187 - Repeated DNA Subsequences

The DNA sequence is composed of a series of nucleotides abbreviated as 'A', 'C', 'G', and 'T'.

• For example, "ACGAATTCCG" is a DNA sequence.

When studying DNA, it is useful to identify repeated sequences within the DNA.

Given a string s that represents a DNA sequence, return all the 10-letter-long sequences (substrings) that occur more than once in a DNA molecule. You may return the answer in any order.

Examples

Input: s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT" Output: ["AAAAACCCCC","CCCCCAAAAA"]

Input: s = "AAAAAAAAAAAAA" Output: ["AAAAAAAAAA"]

Constraints

• 1 <= s.length <= 105

• s[i] is either 'A', 'C', 'G', or 'T'.

Java Solution

class Solution {
    public List<String> findRepeatedDnaSequences(String s) {
        int L = 10, n = s.length();
        HashSet<String> seen = new HashSet(), output = new HashSet();
        
        for (int start = 0; start < n - L + 1; ++start) {
            String tmp = s.substring(start, start + L);
            if (seen.contains(tmp)) output.add(tmp);
            seen.add(tmp);
        }
        return new ArrayList<String>(output);
    }
}