Repeated DNA Sequences - LintCode

描述
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"]

思路
在字符串中，從左到右依次取長度爲10的字符串，將其放入map中，最後統計字符串出現的次數，大於1的，添加到結果。

#ifndef C1335_H
#define C1335_H
#include<iostream>
#include<string>
#include<vector>
#include<map>
using namespace std;
class Solution {
public:
    /**
    * @param s: a string
    * @return: return List[str]
    */
    vector<string> findRepeatedDnaSequences(string &s) {
        // write your code here
        vector<string> res;
        if (s.size() < 10)
            return res;
        map<string, int> m;//存放字符串及其出現的次數
        for (int i = 0; i + 10 <= s.size(); ++i)
            m[s.substr(i, 10)]++;
        for (auto c : m)
        {
            if (c.second>1)
                res.push_back(c.first);
        }
        return res;
    }   
};
#endif