187. Repeated DNA Sequences
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https://leetcode.com/problems/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.
Example:
Input: s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT" Output: ["AAAAACCCCC", "CCCCCAAAAA"]
解题思路:
需要注意的是,因为substring的长度是const的10,所以实际上是O(10n)。
class Solution { public List<String> findRepeatedDnaSequences(String s) { List<String> res = new ArrayList<String>(); if (s.length() < 11) { return res; } StringBuffer sb = new StringBuffer(); Map<String, Integer> map = new HashMap<String, Integer>(); int index = 0; while (index <= s.length() - 10) { String temp = s.substring(index, index + 10); int count = map.getOrDefault(temp, 0); if (count == 1) { res.add(temp); map.put(temp, count + 1); } else if (count == 0){ map.put(temp, 1); } index++; } return res; } }
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