Implement a trie with insert
, search
, and startsWith
methods.
Note:
You may assume that all inputs are consist of lowercase letters a-z
.
思路:实现单词查找树,它是一种树形结构;用于保存大量的字符串。它的优点是:利用字符串的公共前缀来节约存储空间。每个节点有26个从节点。isEndOfWord,children,两个关键变量。
代码如下:
class TrieNode { // Initialize your data structure here. boolean isEndOfWord; TrieNode[] children; public TrieNode() { this.isEndOfWord=false; this.children=new TrieNode[26]; } } public class Trie { private TrieNode root; public Trie() { root = new TrieNode(); } // Inserts a word into the trie. public void insert(String word) { TrieNode runner=root; for(char c:word.toCharArray()){ if(runner.children[c-'a']==null){ runner.children[c-'a']=new TrieNode(); } runner=runner.children[c-'a']; } runner.isEndOfWord=true; } // Returns if the word is in the trie. public boolean search(String word) { TrieNode runner=root; for(char c:word.toCharArray()){ if(runner.children[c-'a']==null){ return false; }else{ runner=runner.children[c-'a']; } } return runner.isEndOfWord; } // Returns if there is any word in the trie // that starts with the given prefix. public boolean startsWith(String prefix) { TrieNode runner=root; for(char c:prefix.toCharArray()){ if(runner.children[c-'a']==null){ return false; }else{ runner=runner.children[c-'a']; } } return true; } } // Your Trie object will be instantiated and called as such: // Trie trie = new Trie(); // trie.insert("somestring"); // trie.search("key");
运行结果: