[Swift]LeetCode187. 重复的DNA序列 | Repeated DNA Sequences

发布时间：2020-12-14 05:08:38 所属栏目：百科来源：网络整理

导读：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 se

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.

Example:

Input: s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT"

Output: ["AAAAACCCCC","CCCCCAAAAA"]

所有 DNA 由一系列缩写为 A，C，G 和 T 的核苷酸组成，例如：“ACGAATTCCG”。在研究 DNA 时，识别 DNA 中的重复序列有时会对研究非常有帮助。

编写一个函数来查找 DNA 分子中所有出现超多一次的10个字母长的序列（子串）。

示例:

输入: s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT"

输出: ["AAAAACCCCC","CCCCCAAAAA"]

超出时间限制

 1 class Solution {
 2     func findRepeatedDnaSequences(_ s: String) -> [String] {
 3         if s.count < 9 {return []}
 4         var res:Set<String> = Set<String>()
 5         var st:Set<String> = Set<String>()
 6         for i in 0..<(s.count - 9)
 7         {
 8             var t:String = s.subString(i,10)
 9             if st.contains(t)
10             {
11                 res.insert(t)
12             }
13             else
14             {
15                 st.insert(t)
16             }
17         }
18         //Set转数组[String]
19         return Array(res)
20     }
21 }
22 
23 extension String {
24     // 截取字符串：指定索引和字符数
25     // - begin: 开始截取处索引
26     // - count: 截取的字符数量
27     func subString(_ begin:Int,_ count:Int) -> String {
28         let start = self.index(self.startIndex,offsetBy: max(0,begin))
29         let end = self.index(self.startIndex,offsetBy:  min(self.count,begin + count))
30         return String(self[start..<end]) 
31     }
32     
33 }

超出时间限制

 1 class Solution {
 2     func findRepeatedDnaSequences(_ s: String) -> [String] {
 3         if s.count < 9 {return []}
 4         var res:Set<String> = Set<String>()
 5         var st:Set<String> = Set<String>()
 6         var cur:Int = 0
 7         for i in 0..<9
 8         {
 9             cur = cur << 3 | (s[i].ascii & 7)
10         }
11         
12         for i in 9..<s.count
13         {
14             cur = ((cur & 0x7ffffff) << 3) | (s[i].ascii & 7)
15             var t:String = s.subString(i - 9,10)
16             if st.contains(t)
17             {
18                 res.insert(t)
19             }
20             else
21             {
22                 st.insert(t)
23             }
24         }
25         
26         //Set转数组[String]
27         return Array(res)
28     }
29 }
30 
31 extension String {
32     //subscript函数可以检索数组中的值
33     //直接按照索引方式截取指定索引的字符
34     subscript (_ i: Int) -> Character {
35         //读取字符
36         get {return self[index(startIndex,offsetBy: i)]}
37     }
38     
39     // 截取字符串：指定索引和字符数
40     // - begin: 开始截取处索引
41     // - count: 截取的字符数量
42     func subString(_ begin:Int,_ count:Int) -> String {
43         let start = self.index(self.startIndex,begin))
44         let end = self.index(self.startIndex,begin + count))
45         return String(self[start..<end]) 
46     }
47     
48 }
49 
50 //Character扩展方法  
51 extension Character  
52 {  
53   //属性：ASCII整数值(定义小写为整数值)
54    var ascii: Int {
55         get {
56             let s = String(self).unicodeScalars
57             return Int(s[s.startIndex].value)
58         }
59     }
60 }

（编辑：李大同）

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