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.
Input: s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT" Output: ["AAAAACCCCC", "CCCCCAAAAA"]
Use a dict to count the number of occurrences of 10-letter sequences.
class Solution(object): def findRepeatedDnaSequences(self, s): """ :type s: str :rtype: List[str] """ if len(s) < 10: return  d = dict() for i in range(len(s) - 9): substr = s[i:i+10] if substr in d: d[substr] += 1 else: d[substr] = 1 return [substr for substr in d if d[substr] > 1]