[leetcode] 187. Repeated DNA Sequences 解题报告

题目链接: 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.

For example,

Given s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT",

Return:
["AAAAACCCCC", "CCCCCAAAAA"].

思路: 一个简单的hash表就可以搞定, 居然这么简单就过了, 也有点太水了吧.

代码如下: 

class Solution {
public:
    vector findRepeatedDnaSequences(string s) {
        if(s.size() < 10) return vector();
        unordered_map hash;
        vector result;
        for(int i = 0; i < s.size()-9; i++)
        {
            string str = s.substr(i, 10);
            if(hash.count(str) && hash[str] < 2)
                result.push_back(str);
            hash[str]++;
        }
        return result;
    }
};