LeetCode-Repeated DNA Sequences

最新推荐文章于 2021-10-10 00:59:49 发布

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#LeetCode #Repeated DNA Sequenc

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本文介绍了一种使用字符转二进制hashtable的方法来解决寻找DNA分子中重复的10字母序列的问题，通过将A,C,G,T分别转换为1,3,2,0并进行20位存储，避免了内存超时的问题，并提供了具体实现代码。

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"].

解题报告：标准字符转二进制的hash table。直接用string进行存储会内存超时。

采用( s[i] - 'A' + 1 ) % 5 )把A,C,G,T,转换为1,3,2,0；t = ( (t<<2) & 0xfffff) | ( ( s[i] - 'A' + 1 ) % 5 );进行20位的存贮。

class Solution {
public:
    vector<string> findRepeatedDnaSequences(string s) {
        vector<string> result;
        unordered_map<int,int> str;
        unordered_map<int,int>::iterator it;
        int t;
        for (int i = 0; i < s.size() ;i++) {
            t = ( (t<<2) & 0xfffff) | ( ( s[i] - 'A' + 1 ) % 5 );
            if (i < 9)  continue;
            it = str.find(t);
            if (it == str.end())
                str[t] = 1;
            else {
                if (str[t] == 1) {
                    str[t] = 2;
                    result.push_back(s.substr(i-9,10));
                }
            }
        }
        return result;
    }
};

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