Tries

Tries are one of my favorite data structures, I've used them often in the past for natural language processing tasks. In Python, a trie is easily implemented as a nested tree of dictionaries where each key is a character that maps to the next character in a word. For example, the words:

hello
help
hi

Would be represented as:

{
	"h": {
		"e": {
			"l": {
				"l": {
					"o": {
						"*": True
					}
				},
				"p": {
					"*": True
				}
			}
		},
		"i": {
			"*": True
		}
	}
}

The * character (paired with True instead of a dictionary) is used to indicate the end of a word.

A trie is also often referred to as a "prefix tree" because it can be used to efficiently find all of the words that start with a given prefix.

Assignment

We're going to use a trie to add "prefix searching" to LockedIn. For example, a user will be able to type "dev" into a job search bar and see the autocomplete suggestions "developer", "development", "devops", etc.

Complete the add method. It takes a word as input, and should add it to the trie.

Keep track of your "current level" in the trie, starting at the root.
Loop over each character in the word-to-add:
1. If the character is not a key in the current level, add it and create a new nested level (dictionary) for it.
2. Update your "current level" to the nested dictionary for this character (whether it was just created or already existed).
Once you've ensured all the dictionaries exist, add the self.end_symbol to the dictionary of the last character in the word. This will indicate that this is a complete word and not just a prefix of another word.