#211 - Design Add and Search Words Data Structure

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Problem Description

Design a data structure that supports adding new words and finding if a string matches any previously added string.

Implement the WordDictionary class:

WordDictionary() Initializes the object.
void addWord(word) Adds word to the data structure, it can be matched later.
bool search(word) Returns true if there is any string in the data structure that matches word or false otherwise. word may contain dots '.' where dots can be matched with any letter.

Solution

var WordDictionary = function() {
  this.root = {};
};

/**
 * @param {string} word
 * @return {void}
 */
WordDictionary.prototype.addWord = function(word) {
  let node = this.root;

  for (const character of word) {
    node[character] = node[character] || {};
    node = node[character];
  }

  node.isTail = true;
};

/**
 * @param {string} word
 * @return {boolean}
 */
WordDictionary.prototype.search = function(word) {
  return dfs(this.root, 0);

  function dfs(node, i) {
    if (word.length === i) {
      return node.isTail;
    }
    if (word[i] === '.') {
      for (const key in node) {
        if (dfs(node[key], i + 1)) {
          return true;
        }
      }
    } else if (node[word[i]] && dfs(node[word[i]], i + 1)) {
      return true;
    }

    return false;
  }
};