208.实现-trie-前缀树.js

/*
 * @lc app=leetcode.cn id=208 lang=javascript
 *
 * [208] 实现 Trie (前缀树)
 */

// @lc code=start
/**
 * Initialize your data structure here.
 */
var Trie = function () {
  this.children = {}
}

/**
 * Inserts a word into the trie.
 * @param {string} word
 * @return {void}
 */
Trie.prototype.insert = function (word) {
  let node = this.children
  for (const ch of word) {
    if (!node[ch]) {
      node[ch] = {}
    }
    node = node[ch]
  }
  node.isEnd = true
}

Trie.prototype.searchPrefix = function (word) {
  let node = this.children
  for (const ch of word) {
    if (!node[ch]) {
      return null
    }
    node = node[ch]
  }
  return node
}

/**
 * Returns if the word is in the trie.
 * @param {string} word
 * @return {boolean}
 */
Trie.prototype.search = function (word) {
  const ret = this.searchPrefix(word)
  return !!(ret && ret.isEnd)
}

/**
 * Returns if there is any word in the trie that starts with the given prefix.
 * @param {string} prefix
 * @return {boolean}
 */
Trie.prototype.startsWith = function (prefix) {
  return !!this.searchPrefix(prefix)
}

/**
 * Your Trie object will be instantiated and called as such:
 * var obj = new Trie()
 * obj.insert(word)
 * var param_2 = obj.search(word)
 * var param_3 = obj.startsWith(prefix)
 */
// @lc code=end