实现前缀树

剑指 Offer II 062. 实现前缀树

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 。

示例：

输入
inputs = ["Trie", "insert", "search", "search", "startsWith", "insert", "search"]
inputs = [[], ["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

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

注意：本题与主站 208 题相同：https://leetcode.cn/problems/implement-trie-prefix-tree/

原站题解

去查看

上次编辑到这里，代码来自缓存点击恢复默认模板

class Trie { public: /** Initialize your data structure here. */ Trie() { } /** Inserts a word into the trie. */ void insert(string word) { } /** Returns if the word is in the trie. */ bool search(string word) { } /** Returns if there is any word in the trie that starts with the given prefix. */ bool startsWith(string prefix) { } }; /** * Your Trie object will be instantiated and called as such: * Trie* obj = new Trie(); * obj->insert(word); * bool param_2 = obj->search(word); * bool param_3 = obj->startsWith(prefix); */

python3 解法, 执行用时: 168 ms, 内存消耗: 33.7 MB, 提交时间: 2022-11-12 11:55:41

class Trie:
    def __init__(self):
        self.children = [None] * 26
        self.isEnd = False
    
    def searchPrefix(self, prefix: str) -> "Trie":
        node = self
        for ch in prefix:
            ch = ord(ch) - ord("a")
            if not node.children[ch]:
                return None
            node = node.children[ch]
        return node

    def insert(self, word: str) -> None:
        node = self
        for ch in word:
            ch = ord(ch) - ord("a")
            if not node.children[ch]:
                node.children[ch] = Trie()
            node = node.children[ch]
        node.isEnd = True

    def search(self, word: str) -> bool:
        node = self.searchPrefix(word)
        return node is not None and node.isEnd

    def startsWith(self, prefix: str) -> bool:
        return self.searchPrefix(prefix) is not None




# Your Trie object will be instantiated and called as such:
# obj = Trie()
# obj.insert(word)
# param_2 = obj.search(word)
# param_3 = obj.startsWith(prefix)

golang 解法, 执行用时: 40 ms, 内存消耗: 15 MB, 提交时间: 2022-11-12 11:47:14

type Trie struct {
    children [26]*Trie
    isEnd    bool
}

func Constructor() Trie {
    return Trie{}
}

func (t *Trie) Insert(word string) {
    node := t
    for _, ch := range word {
        ch -= 'a'
        if node.children[ch] == nil {
            node.children[ch] = &Trie{}
        }
        node = node.children[ch]
    }
    node.isEnd = true
}

func (t *Trie) SearchPrefix(prefix string) *Trie {
    node := t
    for _, ch := range prefix {
        ch -= 'a'
        if node.children[ch] == nil {
            return nil
        }
        node = node.children[ch]
    }
    return node
}

func (t *Trie) Search(word string) bool {
    node := t.SearchPrefix(word)
    return node != nil && node.isEnd
}

func (t *Trie) StartsWith(prefix string) bool {
    return t.SearchPrefix(prefix) != nil
}

/**
 * Your Trie object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Insert(word);
 * param_2 := obj.Search(word);
 * param_3 := obj.StartsWith(prefix);
 */

python3 解法, 执行用时: 848 ms, 内存消耗: 21.9 MB, 提交时间: 2022-11-12 11:43:43

class Trie:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.arr = []


    def insert(self, word: str) -> None:
        """
        Inserts a word into the trie.
        """
        self.arr.append(word)


    def search(self, word: str) -> bool:
        """
        Returns if the word is in the trie.
        """
        return word in self.arr


    def startsWith(self, prefix: str) -> bool:
        """
        Returns if there is any word in the trie that starts with the given prefix.
        """
        for word in self.arr:
            if word.startswith(prefix):
                return True
        return False



# Your Trie object will be instantiated and called as such:
# obj = Trie()
# obj.insert(word)
# param_2 = obj.search(word)
# param_3 = obj.startsWith(prefix)

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