trie

Why are hash maps better than trie maps?

由 社会主义新天地 提交于 2019-11-28 04:00:34
问题 By trie map I mean an associative array, where the payloads are stored in a trie instead of a hash table. When I'm using a hash map/table, the keys I use are typically strings. What are the advantages of a hash map over some trie based map? I have read that a hash map is faster - but it seems to me that a consistent hash functions would have to check each element of the (char) array for the final hash - iterating over the array once. In a trie you would similarly have to iterate over the

Trie complexity and searching

由 ℡╲_俬逩灬. 提交于 2019-11-27 17:20:35
问题 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? 回答1: 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

Trie implementation

由 拈花ヽ惹草 提交于 2019-11-27 13:53:58
问题 I am attempting to implement a very simple Trie in Java that supports 3 operations. I'd like it to have an insert method, a has method (ie is a certain word in the trie), and a toString method to return the trie in string form. I believe I have insertion working properly, but has and toString are proving to be difficult. Here's what I have so far. The trie class. public class CaseInsensitiveTrie implements SimpleTrie { //root node private TrieNode r; public CaseInsensitiveTrie() { r = new

Trie vs. suffix tree vs. suffix array

由 元气小坏坏 提交于 2019-11-27 10:26:20
Which structure provides the best performance results; trie (prefix tree), suffix tree or suffix array? Are there other similar structures? What are good Java implementations of these structures? Edit: in this case I want to make string matching between a large dictionary of names and a large set of natural language texts, in order to identify the names of the dictionary on texts. Miguel Figueiredo The trie was the first data structure of this kind discovered. The suffix tree is an improvement over the trie (it has suffix links which allow linear error search, the suffix tree trims unnecessary

Implementing a Patricia Trie for use as a dictionary

由 [亡魂溺海] 提交于 2019-11-27 10:23:47
问题 I'm attempting to implement a Patricia Trie with the methods addWord() , isWord() , and isPrefix() as a means to store a large dictionary of words for quick retrieval (including prefix search). I've read up on the concepts but they just aren't clarifying into an implementation. I want to know (in Java or Python code) how to implement the Trie, particularly the nodes (or should I implement it recursively). I saw one person who implemented it with an array of 26 child nodes set to null/None. Is

Longest Prefix Matches for URLs

由 半世苍凉 提交于 2019-11-27 10:03:25
问题 I need information about any standard python package which can be used for "longest prefix match" on URLs. I have gone through the two standard packages http://packages.python.org/PyTrie/#pytrie.StringTrie & 'http://pypi.python.org/pypi/trie/0.1.1' but they don't seem to be useful for longest prefix match task on URLs. Examlple, if my set has these URLs 1->http://www.google.com/mail , 2->http://www.google.com/document, 3->http://www.facebook.com, etc.. Now if I search for 'http://www.google

Autocomplete using a trie

由 强颜欢笑 提交于 2019-11-27 00:15:34
问题 I am working on an autocompletion script and was thinking about using a trie. My problem is I want everything that matches to be returned. So for example I type in the letter r I want all entries starting with r to be returned. Then all entries starting with re etc. Is this feasible with a trie and how would it work. Also, if there is a better way I am open to suggestions. The reason I ask is it seems like it would be complicated and a whole lot of processing to return all of the nodes off of

How Do I Choose Between a Hash Table and a Trie (Prefix Tree)?

由 孤街浪徒 提交于 2019-11-26 21:09:43
So if I have to choose between a hash table or a prefix tree what are the discriminating factors that would lead me to choose one over the other. From my own naive point of view it seems as though using a trie has some extra overhead since it isn't stored as an array but that in terms of run time (assuming the longest key is the longest english word) it can be essentially O(1) (in relation to the upper bound). Maybe the longest english word is 50 characters? Hash tables are instant look up once you get the index . Hashing the key to get the index however seems like it could easily take near 50

How to create a trie in c#

由 不羁的心 提交于 2019-11-26 19:37:17
Does anyone know where I can find an example of how to construct a trie in C#. I'm trying to take a dictionary/list of words and create a trie with it. Fantius This is my own code, pulled from my answer to How to find a word from arrays of characters? : public class Trie { public struct Letter { public const string Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; public static implicit operator Letter(char c) { return new Letter() { Index = Chars.IndexOf(c) }; } public int Index; public char ToChar() { return Chars[Index]; } public override string ToString() { return Chars[Index].ToString(); } } public

Trie vs. suffix tree vs. suffix array

由 倾然丶 夕夏残阳落幕 提交于 2019-11-26 17:56:28
问题 Which structure provides the best performance results; trie (prefix tree), suffix tree or suffix array? Are there other similar structures? What are good Java implementations of these structures? Edit: in this case I want to make string matching between a large dictionary of names and a large set of natural language texts, in order to identify the names of the dictionary on texts. 回答1: The trie was the first data structure of this kind discovered. The suffix tree is an improvement over the
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