187. Repeated DNA Sequences

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.

 

由于英文差劲，真的读了半天才明白题意思。

就是查找DNA分子中所有10个字母长的字串且字串不止出现一次。

 

附leetcode中StefanPochmann的解。用两个hashset，简单易懂。

public List findRepeatedDnaSequences(String s) {
        Set seen = new HashSet(), repeated = new HashSet();
        for (int i = 0; i + 9 < s.length(); i++) {
            String ten = s.substring(i, i + 10);
            if (!seen.add(ten)) {                
                repeated.add(ten);
            }
        }
    //    System.out.println(seen.toString());
        
        return new ArrayList(repeated);
    }