leetcode Repeated DNA Sequences 哈希表

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"].

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Hash Table Bit
Manipulation

题目意思是有一个DNA序列，10个为一串，找到重复的串，刚开始用map存string，然后超内存，然后看标签知道要用位运算，但是每次都是先存在一个stirng中，再转为二进制，超时，其实每次加新的时候前9个是已知的，再通过位运算接上就行了。

class Solution {
public:
	int change(char x)
	{
		if (x == 'A') return 0;
		if (x == 'T') return 1;
		if (x == 'C') return 2;
		if (x == 'G') return 3;
	}
	vector<string> findRepeatedDnaSequences(string s) {
		vector<string>res;
		string temp;
		unsigned int n=0;
		map<int, int>Hash;
		int size = s.size();
		if (size < 11) return res;
		for (int i = 0; i < 10; i++)
		{
			n = n << 2;
			n = n | change(s[i]);
		}
		Hash
 = 0;
		for (int j = 10; j < size; j++)
		{
			n = n << 14;
			n = n >> 12;
			n = n | change(s[j]);
			if (Hash.find(n) != Hash.end())//防止出现多次而添加多次
			{
				if (Hash
 == 0)
				{
					Hash
 = -1;
					temp = s.substr(j - 9, 10);
					res.push_back(temp);
				}
			}
			else
			{
				Hash
 = 0;
			}

		}
			
		return res;
	}
};