Do, or do not there is no trie

1
Do, or do not there is no trie

• With apologies to George Lucas, and more
  importantly to Yoda.

2
What is a trie?

• Trie is a recursive structure.
• Each node in the trie will refer to another trie.

3
Trie class

• Has an instance variable for an array that will
  hold elements of type Trie
• private Trie _trieNodes
• boolean variable to signify whether or not the
  particular trie/node (remember that each node IS
  a trie) is a valid end of word.
• Initialized to false at first.

4
Trie Class Methods

• Helper method to convert a character to an int
  index.
• While not strictly required, will be beneficial.
• This method should map a given character to its
  appropriate array index. A0, B1, etc.

5
Method to add a word to the trie

• Every word in the dictionary file must be added
  to the trie.
• void addWord(String word)
• Throughout the method, a local variable of type
  Trie is recommended to keep track of where you
  are in the overall Trie. Remember that each part
  of the subtree(ie) is a trie itself.
• Trie workingTrie
• Start at the root of the trie - store it in
  workingTrie.

6
Method to add a word to the trie

• In a loop
• Parse string character by character and convert
  character to index
• If element at index is null,
• Create a new Trie and store it at index
• Set workingTrie to the trie at the character
  index of the current level
• workingTrie workingTrie._trieNodesindex
• Once the end of the word is reached, set the
  boolean to true since this node represents a
  valid/actual word.

7
Method to add a word to the trie

• Note that the actual character is never
  explicitly stored in the trie.
• If desired, you could store the character,
  however it is not necessary. If a given index is
  null, that particular character is not in the
  current level of the trie. If the index contains
  an element (a trie) than it is in the current
  level.

8
Method to test whether a given string is a valid
word found in the trie

• boolean isWord(String word)
• Same basic structure of the addWord(..) method
• Parse string character by character
• If a given index is not found, word is not valid
• If the string is fully parsed return the value of
  the boolean of that node.
• The boolean will be false if it not a valid end
  of word, and true if it is a valid word.