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"].
比较经典的题目
思路：用hashmap扫一遍，出现过的就加到list上去，为了不使结果重复，当碰到重复的时候更新value。
public class Solution { public List<String> findRepeatedDnaSequences(String s) { List<String> res=new ArrayList<>(); if(s==null)return res; Map<String,Integer> check=new HashMap<>(); for(int i=0;i<=s.length()-10;i++){ String sub=s.substring(i,i+10); if(!check.containsKey(sub)){ check.put(sub,1); }else{ if(check.get(sub)==1){ res.add(sub); check.put(sub,2); } } } return res; } }
原文：http://www.cnblogs.com/Machelsky/p/5955894.html