做题博客链接
https://blog.youkuaiyun.com/qq_43349112/article/details/108542248
题目链接
https://leetcode-cn.com/problems/implement-trie-prefix-tree/
描述
Trie(发音类似 "try")或者说 前缀树 是一种树形数据结构,用于高效地存储和检索字符串数据集中的键。这一数
据结构有相当多的应用情景,例如自动补完和拼写检查。
请你实现 Trie 类:
Trie() 初始化前缀树对象。
void insert(String word) 向前缀树中插入字符串 word 。
boolean search(String word) 如果字符串 word 在前缀树中,返回 true(即,在检索之前已经插入);否则,返
回 false 。
boolean startsWith(String prefix) 如果之前已经插入的字符串 word 的前缀之一为 prefix ,返回 true ;否
则,返回 false 。
提示:
1 <= word.length, prefix.length <= 2000
word 和 prefix 仅由小写英文字母组成
insert、search 和 startsWith 调用次数 总计 不超过 3 * 104 次
示例
输入
["Trie", "insert", "search", "search", "startsWith", "insert", "search"]
[[], ["apple"], ["apple"], ["app"], ["app"], ["app"], ["app"]]
输出
[null, null, true, false, true, null, true]
解释
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
初始代码模板
class Trie {
/** Initialize your data structure here. */
public Trie() {
}
/** Inserts a word into the trie. */
public void insert(String word) {
}
/** Returns if the word is in the trie. */
public boolean search(String word) {
}
/** Returns if there is any word in the trie that starts with the given prefix. */
public boolean startsWith(String prefix) {
}
}
/**
* 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);
*/
代码
前缀树模板题。
推荐题解:
https://leetcode-cn.com/problems/implement-trie-prefix-tree/solution/shi-xian-trie-qian-zhui-shu-by-leetcode-ti500/
class Trie {
private boolean isEnd;
private Trie[] children;
/** Initialize your data structure here. */
public Trie() {
this.isEnd = false;
this.children = new Trie[26];
}
/** Inserts a word into the trie. */
public void insert(String word) {
Trie trie = this;
for (int i = 0; i < word.length(); i++) {
char c = word.charAt(i);
int idx = c - 'a';
if (trie.children[idx] == null) {
trie.children[idx] = new Trie();
}
trie = trie.children[idx];
}
trie.isEnd = true;
}
/** Returns if the word is in the trie. */
public boolean search(String word) {
Trie res = searchWord(word);
return res != null && res.isEnd;
}
/** Returns if there is any word in the trie that starts with the given prefix. */
public boolean startsWith(String prefix) {
Trie res = searchWord(prefix);
return res != null;
}
private Trie searchWord(String word) {
Trie trie = this;
for (int i = 0; i < word.length(); i++) {
char c = word.charAt(i);
int idx = c - 'a';
if (trie.children[idx] == null) {
return null;
}
trie = trie.children[idx];
}
return trie;
}
}
/**
* 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);
*/