[leetcode]Repeated DNA Sequences

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本文介绍了一种使用二进制表示和哈希表来查找DNA分子中长度为10且重复出现的序列的方法。通过将每个核苷酸转换为3位二进制数，并维护一个大小为2^30的哈希表，可以高效地识别出所有符合条件的重复序列。

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.

二进制表示+哈希表
表示十个字母需要30位二进制数，开2^30的哈希表记录

class Solution {
public:
    vector<string> findRepeatedDnaSequences(string s) {
        vector<string> str;
        map<int,int> m;
        int i,cur=0;
        for(i=0;i<10;i++){
            cur <<= 3;
            cur |= (s[i] & 7);
        }
        m[cur] = 1;
        for(i=10;i<s.size();i++){
            cur <<= 3;
            cur |= (s[i] & 7);
            cur &= 0x3fffffff;
            if(m.find(cur)!=m.end()){
                if(m[cur] == 1) str.push_back(s.substr(i-9,10));
                m[cur] ++;
            }
            else{
                m[cur] = 1;
            }
        }

        return str;

    }

};