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Implement a trie with insert, search, and startsWith methods.
Note:
You may assume that all inputs are consist of lowercase letters a-z.
解题思路：
参考百度百科：Trie树
已经给出了详细的代码：
JAVA实现如下：
class TrieNode {
// Initialize your data structure here.
int num;// 有多少单词通过这个节点,即节点字符出现的次数
TrieNode[] son;// 所有的儿子节点
boolean isEnd;// 是不是最后一个节点
char val;// 节点的值
TrieNode() {
this.num = 1;
this.son = new TrieNode[26];
this.isEnd = false;
}
}
public class Trie {
private TrieNode root;
public Trie() {
root = new TrieNode();
}
public void insert(String word) {
if (word == null || word.length() == 0)
return;
TrieNode node = this.root;
char[] letters = word.toCharArray();
for (int i = 0; i < word.length(); i++) {
int pos = letters[i] - ‘a‘;
if (node.son[pos] == null) {
node.son[pos] = new TrieNode();
node.son[pos].val = letters[i];
} else {
node.son[pos].num++;
}
node = node.son[pos];
}
node.isEnd = true;
}
// Returns if the word is in the trie.
public boolean search(String word) {
if (word == null || word.length() == 0) {
return false;
}
TrieNode node = root;
char[] letters = word.toCharArray();
for (int i = 0; i < word.length(); i++) {
int pos = letters[i] - ‘a‘;
if (node.son[pos] != null) {
node = node.son[pos];
} else {
return false;
}
}
return node.isEnd;
}
// Returns if there is any word in the trie
// that starts with the given prefix.
public boolean startsWith(String prefix) {
if (prefix == null || prefix.length() == 0) {
return false;
}
TrieNode node = root;
char[] letters = prefix.toCharArray();
for (int i = 0; i < prefix.length(); i++) {
int pos = letters[i] - ‘a‘;
if (node.son[pos] != null) {
node = node.son[pos];
} else {
return false;
}
}
return true;
}
}
// Your Trie object will be instantiated and called as such:
// Trie trie = new Trie();
// trie.insert("somestring");
// trie.search("key");
Java for LeetCode 208 Implement Trie (Prefix Tree)
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原文地址：http://www.cnblogs.com/tonyluis/p/4563990.html
