LeetCode-Repeated DNA Sequences - c++编程基础

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
  
    findRepeatedDnaSequences(string s) {
        vector
   
     result; unordered_map
    
      str; unordered_map
     
      ::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; } };