Implement Trie (Prefix Tree)

题目描述：

A trie (pronounced as “try”) or prefix tree is a tree data structure used to efficiently store and retrieve keys in a dataset of strings. There are various applications of this data structure, such as autocomplete and spellchecker.

Implement the Trie class:

Trie() Initializes the trie object.
void insert(String word) Inserts the string word into the trie.
boolean search(String word) Returns true if the string word is in the trie (i.e., was inserted before), and false otherwise.
boolean startsWith(String prefix) Returns true if there is a previously inserted string word that has the prefix prefix, and false otherwise.

Example 1:

Input
[“Trie”, “insert”, “search”, “search”, “startsWith”, “insert”, “search”]
[[], [“apple”], [“apple”], [“app”], [“app”], [“app”], [“app”]]
Output
[null, null, true, false, true, null, true]

Explanation
Trie trie = new Trie();
trie.insert(“apple”);
trie.search(“apple”); // return True
trie.search(“app”); // return False
trie.startsWith(“app”); // return True
trie.insert(“app”);
trie.search(“app”); // return True

Constraints:

1 <= word.length, prefix.length <= 2000
word and prefix consist only of lowercase English letters.
At most 3 * 104 calls in total will be made to insert, search, and startsWith.

思路:

26叉树，知道了之后不难

代码:

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


func Constructor() Trie {
    return Trie{}
}


func (this *Trie) Insert(word string)  {
        trie := this
        for i:=0;i<len(word); i++{
            if trie.children[word[i]-'a'] == nil{
                trie.children[word[i]-'a'] = new(Trie)
            }
            
            trie = trie.children[word[i]-'a']
        }
        trie.isEnd = true
}


func (this *Trie) Search(word string) bool {
    trie := this
    for i:=0;i<len(word);i++{
        if trie.children[word[i] - 'a'] == nil{
            return false
        }
        trie = trie.children[word[i] - 'a']
    }
    return trie.isEnd
}


func (this *Trie) StartsWith(prefix string) bool {
    trie := this
    for i:=0;i<len(prefix);i++{
        if trie.children[prefix[i] - 'a'] == nil{
            return false
        }
        trie = trie.children[prefix[i] - 'a']
    }
    return true
}


/**
 * 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);
 */

代码效率：

执行用时：44 ms, 在所有 Go 提交中击败了96.45%的用户
内存消耗：18 MB, 在所有 Go 提交中击败了21.89%的用户