Trie complexity and searching
What is the complexity of creating a trie of a list of words and what is complexity of searching other set of word in that trie? Should I use trie for string searching, when i have hashtable?
Answer
The complexity of creating a trie is O(W*L), where W is the number of words, and L is an average length of the word: you need to perform L lookups on the average for each of the W words in the set.
Same goes for looking up words later: you perform L steps for each of the W words.
Hash insertions and lookups have the same complexity: for each word you need to check equality, which takes O(L), for the overall complexity of O(W*L).
If you need to look up entire words, hash table is easier. However, you cannot look up words by their prefix using a hash table; If prefix-based lookups are of no interest to you, use a hash table; otherwise, use a trie.