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”].
一刷ac 解題思路：遍歷字符串，按長度10截取字符串，判斷截取的子串是否截取過，分別將遍歷的結果和重復的串放在兩個set中，返回結果。
public class Solution { public List<String> 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.contains(ten)){ repeated.add(ten); }else seen.add(ten); } return new ArrayList(repeated); }}新聞熱點
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