Leetcode - Longest Palindrome
Leetcode - Word Search II

Leetcode - Implement Trie (Prefix Tree)

violet posted @ Mar 27, 2020 06:59:00 AM in 算法 with tags Algorithm Golang Trie , 41 阅读

https://leetcode.com/problems/implement-trie-prefix-tree/

Implement a trie with insert, search, and startsWith methods.

Example:

Trie trie = new Trie();

trie.insert("apple");
trie.search("apple");   // returns true
trie.search("app");     // returns false
trie.startsWith("app"); // returns true
trie.insert("app");   
trie.search("app");     // returns true

Note:

  • You may assume that all inputs are consist of lowercase letters a-z.
  • All inputs are guaranteed to be non-empty strings.

 

type Trie struct {
    Head *Trie
    Children []*Trie
    Leaf bool
}


/** Initialize your data structure here. */
func Constructor() Trie {
    return Trie{
        Head: &Trie{
            Children: make([]*Trie, 26),
        },
    }
}


/** Inserts a word into the trie. */
func (this *Trie) Insert(word string)  {
    node := this.Head
    for i := 0; i < len(word); i++ {
        index := word[i] - 'a'
        if node.Children[index] == nil {
            node.Children[index] = &Trie{
                Children: make([]*Trie, 26),
            }
        }
        
        node = node.Children[index]
    }
    node.Leaf = true
}


/** Returns if the word is in the trie. */
func (this *Trie) Search(word string) bool {
    node := this.Head
    for i := 0; i < len(word); i++ {
        index := word[i] - 'a'
        if node.Children[index] == nil {
            return false
        }
        node = node.Children[index]
    }

    if !node.Leaf {
        return false
    }
    
    return true
}


/** Returns if there is any word in the trie that starts with the given prefix. */
func (this *Trie) StartsWith(prefix string) bool {
    node := this.Head
    for i := 0; i < len(prefix); i++ {
        index := prefix[i] - 'a'
        if node.Children[index] == nil {
            return false
        }
        node = node.Children[index]
    }
    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);
 */

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