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 somek >= 1, the lastkcharacters queried (in order from oldest to newest, including this letter just queried) spell one of the words in the given list.
Example:
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 wordlistNote:
1 <= words.length <= 20001 <= 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 <= 20001 <= 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。
2156ms
1 let alphaMap: [Character: Int] = [ 2 "a": 0, 3 "b": 1, 4 "c": 2, 5 "d": 3, 6 "e": 4, 7 "f": 5, 8 "g": 6, 9 "h": 7, 10 "i": 8, 11 "j": 9, 12 "k": 10, 13 "l": 11, 14 "m": 12, 15 "n": 13, 16 "o": 14, 17 "p": 15, 18 "q": 16, 19 "r": 17, 20 "s": 18, 21 "t": 19, 22 "u": 20, 23 "v": 21, 24 "w": 22, 25 "x": 23, 26 "y": 24, 27 "z": 25 28 ] 29 30 class Node { 31 var val: Character 32 var next: Node? 33 var prev: Node? 34 35 init(_ val: Character) { 36 self.val = val 37 } 38 } 39 40 41 class LinkedList { 42 private(set) var head = Node(".") 43 private(set) var tail = Node(".") 44 45 init() { 46 head.next = tail 47 tail.prev = head 48 } 49 50 func add(node: Node) { 51 node.next = head.next 52 node.prev = head 53 head.next?.prev = node 54 head.next = node 55 } 56 57 func removeLast() { 58 tail.prev?.prev?.next = tail 59 tail.prev = tail.prev?.prev 60 } 61 62 func snapshot() { 63 var node = head.next 64 var str = "" 65 while let n = node, 66 n !== tail { 67 str += "\(n.val)" 68 node = n.next 69 if node !== tail { 70 str += " -> " 71 } 72 } 73 } 74 } 75 76 class Trie { 77 private(set) var nodes: [Trie?] = [nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil] 78 var isEnd = false 79 80 func add(character: Character) -> Trie? { 81 let index = alphaMap[character]! 82 if nodes[index] == nil { 83 nodes[index] = Trie() 84 } 85 return nodes[index] 86 } 87 88 func find(character: Character) -> Trie? { 89 let index = alphaMap[character]! 90 return nodes[index] 91 } 92 } 93 94 class StreamChecker { 95 96 private var trie = Trie() 97 private var buffer = LinkedList() 98 private var bufferCount = 0 99 private var maxCount = 0 100 101 init(_ words: [String]) { 102 for word in words { 103 var currentTrie: Trie? = trie 104 var count = 0 105 for char in word.reversed() { 106 currentTrie = currentTrie?.add(character: char) 107 count += 1 108 } 109 maxCount = max(maxCount, count) 110 currentTrie?.isEnd = true 111 } 112 } 113 114 func query(_ letter: Character) -> Bool { 115 buffer.add(node: Node(letter)) 116 bufferCount += 1 117 if bufferCount > maxCount { 118 bufferCount -= 1 119 buffer.removeLast() 120 } 121 var node = buffer.head.next 122 var currentTrie: Trie? = trie 123 while let n = node, n !== buffer.tail, let trie = currentTrie { 124 currentTrie = trie.find(character: n.val) 125 if currentTrie?.isEnd ?? false { return true } 126 node = n.next 127 } 128 return false 129 } 130 }
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 */
