Implement the StreamChecker class as follows:

  • StreamChecker(words): Constructor, init the data structure with the given words.
  • query(letter): returns true if and only if for some k >= 1, the last k characters queried (in order from oldest to newest, including this letter just queried) spell one of the words in the given list.

Example:

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StreamChecker streamChecker = new StreamChecker(["cd","f","kl"]); // init the dictionary.
streamChecker.query('a');          // return false
streamChecker.query('b');          // return false
streamChecker.query('c');          // return false
streamChecker.query('d');          // return true, because 'cd' is in the wordlist
streamChecker.query('e');          // return false
streamChecker.query('f');          // return true, because 'f' is in the wordlist
streamChecker.query('g');          // return false
streamChecker.query('h');          // return false
streamChecker.query('i');          // return false
streamChecker.query('j');          // return false
streamChecker.query('k');          // return false
streamChecker.query('l');          // return true, because 'kl' is in the wordlist

Note:

  • 1 <= words.length <= 2000
  • 1 <= words[i].length <= 2000
  • Words will only consist of lowercase English letters.
  • Queries will only consist of lowercase English letters.
  • The number of queries is at most 40000.

按下述要求实现 StreamChecker 类：

  • StreamChecker(words)：构造函数，用给定的字词初始化数据结构。
  • query(letter)：如果存在某些 k >= 1，可以用查询的最后 k个字符（按从旧到新顺序，包括刚刚查询的字母）拼写出给定字词表中的某一字词时，返回 true。否则，返回 false。

示例：

StreamChecker streamChecker = new StreamChecker(["cd","f","kl"]); // 初始化字典
streamChecker.query('a');          // 返回 false
streamChecker.query('b');          // 返回 false
streamChecker.query('c');          // 返回 false
streamChecker.query('d');          // 返回 true，因为 'cd' 在字词表中
streamChecker.query('e');          // 返回 false
streamChecker.query('f');          // 返回 true，因为 'f' 在字词表中
streamChecker.query('g');          // 返回 false
streamChecker.query('h');          // 返回 false
streamChecker.query('i');          // 返回 false
streamChecker.query('j');          // 返回 false
streamChecker.query('k');          // 返回 false
streamChecker.query('l');          // 返回 true，因为 'kl' 在字词表中。

提示：

  • 1 <= words.length <= 2000
  • 1 <= words[i].length <= 2000
  • 字词只包含小写英文字母。
  • 待查项只包含小写英文字母。
  • 待查项最多 40000 个。
Runtime: 2240 ms Memory Usage: 32.3 MB 
 1 class StreamChecker {
 2     var root:TrieNode?
 3     var stream:[Int]
 4     init(_ words: [String]) {
 5         stream = [Int]()
 6         root = TrieNode()
 7         for word in words
 8         {
 9             var arrWord:[Int] = Array(word).map{$0.ascii - 97}
10             var m:Int = word.count
11             var cur:TrieNode? = root
12             for i in stride(from:m - 1,through:0,by:-1)
13             {
14                 if cur?.children[arrWord[i]] == nil
15                 {
16                     cur?.children[arrWord[i]] = TrieNode()
17                 }
18                 cur = cur?.children[arrWord[i]]
19             }            
20             cur?.is_word = true;
21         }        
22     }
23     
24     func query(_ letter: Character) -> Bool {
25         stream.append(letter.ascii)
26         var m:Int = stream.count
27         var cur:TrieNode? = root
28         for i in stride(from:m - 1,through:0,by:-1)
29         {
30             cur = cur?.children[stream[i] - 97]
31             if cur == nil {return false}
32             else if cur!.is_word {return true}
33         }
34         return false
35     }
36 }
37 
38 class TrieNode{
39     var is_word:Bool
40     var children:[TrieNode?]
41     init()
42     {
43         is_word = false
44         children = [TrieNode?](repeating:nil,count:26)
45     }
46 }
47 
48 //Character扩展 
49 extension Character  
50 {  
51   //Character转ASCII整数值(定义小写为整数值)
52    var ascii: Int {
53        get {
54            return Int(self.unicodeScalars.first?.value ?? 0)
55        }       
56     }
57 }
58 
59 /**
60  * Your StreamChecker object will be instantiated and called as such:
61  * let obj = StreamChecker(words)
62  * let ret_1: Bool = obj.query(letter)
63  */

 

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