文章目錄

• 題目描述
• 思路 & 代碼
• • • 更新版

題目描述

• 屬于那種，敲過一遍就不會忘了的那種題，就是學一個新的數(shù)據(jù)結(jié)構= =
• 二十六叉樹！
  

思路 & 代碼

• isEnd 非常重要噢，只有正式 insert 了的單詞才能被 search 到。
• 在 Trie 中實現(xiàn)內(nèi)部類 TrieNode
• 說實話，insert、search、startWith 三個函數(shù)的結(jié)構都十分相似= =
• 注意 new Node 的時候小心。。引用丟失就難受了

class Trie {private class TrieNode{boolean isEnd;TrieNode[] next;TrieNode(){isEnd = false;next = new TrieNode[26];}}private TrieNode root;/** Initialize your data structure here. */public Trie() {root = new TrieNode();}/** Inserts a word into the trie. */// 沒則插，結(jié)尾改 true （出現(xiàn)了，但是沒真正 insert 的話，不算：比如 insert apple , 然后 search app = falsepublic void insert(String word) {char[] wordC = word.toCharArray();TrieNode nowNode = root;for(int i = 0; i < wordC.length; i++){// error：TrieNode nextNode = nowNode.next[wordC[i] - 'a']; nextNode = new TrieNode()// 會直接丟失引用！int index = wordC[i] - 'a';if(nowNode.next[index] == null){nowNode.next[index] = new TrieNode();}nowNode = nowNode.next[index];}// 結(jié)束，標志單詞結(jié)尾字符nowNode.isEnd = true;}/** Returns if the word is in the trie. */public boolean search(String word) {char[] wordC = word.toCharArray();TrieNode nowNode = root;for(int i = 0; i < wordC.length; i++){int index = wordC[i] - 'a';if(nowNode.next[index] == null){return false;}nowNode = nowNode.next[index];}return nowNode.isEnd;}/** Returns if there is any word in the trie that starts with the given prefix. */public boolean startsWith(String prefix) {char[] wordC = prefix.toCharArray();TrieNode nowNode = root;for(int i = 0; i < wordC.length; i++){int index = wordC[i] - 'a';if(nowNode.next[index] == null){return false;}nowNode = nowNode.next[index];}return true;} }/*** Your Trie object will be instantiated and called as such:* Trie obj = new Trie();* obj.insert(word);* boolean param_2 = obj.search(word);* boolean param_3 = obj.startsWith(prefix);*/

更新版

• 其實三個函數(shù)的代碼都差不多= =
• 前綴樹：存儲字符串的一種樹結(jié)構（二十六叉樹），可以實現(xiàn)拼寫檢查、自動補全功能。

class Trie {TrieNode root;private class TrieNode {boolean isEnd;TrieNode[] nextNode;public TrieNode() {isEnd = false;nextNode = new TrieNode[26];}}public Trie() {root = new TrieNode();}public void insert(String word) {TrieNode nowNode = root;for(char c : word.toCharArray()) {int index = c - 'a';if(nowNode.nextNode[index] == null) {nowNode.nextNode[index] = new TrieNode();}nowNode = nowNode.nextNode[index];}nowNode.isEnd = true;}public boolean search(String word) {TrieNode nowNode = root;for(char c : word.toCharArray()) {int index = c - 'a';if(nowNode.nextNode[index] == null) {return false;}nowNode = nowNode.nextNode[index];}return nowNode.isEnd;}public boolean startsWith(String prefix) {TrieNode nowNode = root;for(char c : prefix.toCharArray()) {int index = c - 'a';if(nowNode.nextNode[index] == null) {return false;}nowNode = nowNode.nextNode[index];}return true;} }

總結(jié)

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