[LeetCode] 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"].

用Map的话超内存了,改用bitsmap,因为只有4个字母,所以只要用两位就可以做为一个字母的编码,10个字母就是20位,所以创建一个2^20大小的数组就可以解决问题了。

 1 class Solution {
 2 public:
 3     int getVal(char ch) {
 4         if (ch == 'A') return 0;
 5         if (ch == 'C') return 1;
 6         if (ch == 'G') return 2;
 7         if (ch == 'T') return 3;
 8     }
 9     
10     vector<string> findRepeatedDnaSequences(string s) {
11         set<string> st;
12         vector<string> res;
13         string str;
14         if (s.length() < 10 || s == "") return res;
15         int mp[1024*1024] = {0};
16         unsigned int val = 0;
17         for (int i = 0; i < 9; ++i) {
18             val <<= 2;
19             val |= getVal(s[i]);
20         }
21         for (int i = 9; i < s.length(); ++i) {
22             val <<= 14;
23             val >>= 12;
24             val |= getVal(s[i]);
25             ++mp[val];
26             if (mp[val] > 1) {
27                 str = s.substr(i-9, 10);
28                 st.insert(str);
29             }
30         }
31         for (set<string>::iterator i = st.begin(); i != st.end(); ++i) {
32             res.push_back(*i);
33         }
34         return res;
35     }
36 };

 

posted @ 2015-03-07 21:11  Eason Liu  阅读(1791)  评论(1编辑  收藏  举报