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Copy pathPrefixTrie208.java
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122 lines (104 loc) · 3.04 KB
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//实现一个 Trie (前缀树)，包含 insert, search, 和 startsWith 这三个操作。
//
// 示例:
//
// Trie trie = new Trie();
//
//trie.insert("apple");
//trie.search("apple"); // 返回 true
//trie.search("app"); // 返回 false
//trie.startsWith("app"); // 返回 true
//trie.insert("app");
//trie.search("app"); // 返回 true
//
// 说明:
//
//
// 你可以假设所有的输入都是由小写字母 a-z 构成的。
// 保证所有输入均为非空字符串。
//
// Related Topics 设计 字典树
// 👍 418 👎 0
//leetcode submit region begin(Prohibit modification and deletion)
class PrefixTrie208 {
class TrieNode {
private TrieNode[] links;
private final int R = 26;
private boolean isEnd;
/**
* Initialize your data structure here.
*/
public TrieNode() {
links = new TrieNode[R];
}
public boolean containKey(char ch) {
return links[ch - 'a'] != null;
}
public TrieNode get(char ch) {
return links[ch - 'a'];
}
public void put(char ch, TrieNode node) {
links[ch - 'a'] = node;
}
public boolean isEnd() {
return isEnd;
}
public void setEnd() {
isEnd = true;
}
}
class Trie {
private TrieNode root;
public Trie() {
root = new TrieNode();
}
/**
* Inserts a word into the trie.
*/
public void insert(String word) {
TrieNode node = root;
for (int i = 0; i < word.length(); i++) {
char currentchar = word.charAt(i);
if (!node.containKey(currentchar)) {
node.put(currentchar, new TrieNode());
}
node = node.get(currentchar);
}
node.setEnd();
}
/**
* Returns if the word is in the trie.
*/
public boolean search(String word) {
TrieNode node = searchPrefix(word);
return node != null && node.isEnd();
}
private TrieNode searchPrefix(String prefix) {
TrieNode node = root;
for (int i = 0; i < prefix.length(); i++) {
char currentchar = prefix.charAt(i);
if (node.containKey(currentchar)) {
node = node.get(currentchar);
} else {
return null;
}
}
return node;
}
/**
* Returns if there is any word in the trie that starts with the given prefix.
*/
public boolean startsWith(String prefix) {
TrieNode node = searchPrefix(prefix);
return node != null;
}
}
}
/**
* 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);
*/
//leetcode submit region end(Prohibit modification and deletion)