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.
For example,
Given s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT",
Return:
["AAAAACCCCC", "CCCCCAAAAA"].
解法
維護兩個hashset。
public class Solution {
public List<String> findRepeatedDnaSequences(String s) {
List<String> ret = new ArrayList<>();
if (s == null || s.length() < 10) {
return ret;
}
Set<String> set = new HashSet<String>();
Set<String> repet = new HashSet<String>();
for (int i = 0; i < s.length() - 9; i++) {
String sub = s.substring(i, i + 10);
if (!set.add(sub)) {
repet.add(sub);
}
}
return new ArrayList<>(repet);
}
}