后缀树和尝试。有什么区别吗?

我正在阅读有关 Tries通常被称为前缀树和 Suffix Trees
尽管我已经找到了 Trie的代码,但是我找不到 Suffix Tree的示例。我还感觉到构建 Trie的代码与构建 Suffix Tree的代码是一样的,只是前者存储前缀,而后者存储后缀。
这是真的吗? 有没有人能帮助我在脑海中理清这个问题? 一个示例代码将是很大的帮助!

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A suffix tree can be viewed as a data structure built on top of a trie where, instead of just adding the string itself into the trie, you would also add every possible suffix of that string. As an example, if you wanted to index the string banana in a suffix tree, you would build a trie with the following strings:

banana
anana
nana
ana
na
a

Once that's done you can search for any n-gram and see if it is present in your indexed string. In other words, the n-gram search is a prefix search of all possible suffixes of your string.

This is the simplest and slowest way to build a suffix tree. It turns out that there are many fancier variants on this data structure that improve on either or both space and build time. I'm not well versed enough in this domain to give an overview but you can start by looking into suffix arrays or this class advanced data structures (lecture 16 and 18).

This answer also does a wonderfull job explaining a variant of this data-structure.

If you imagine a Trie in which you put some word's suffixes, you would be able to query it for the string's substrings very easily. This is the main idea behind suffix tree, it's basically a "suffix trie".

But using this naive approach, constructing this tree for a string of size n would be O(n^2) and take a lot of memory.

Since all the entries of this tree are suffixes of the same string, they share a lot of information, so there are optimized algorithms that allows you to create them more efficiently. Ukkonen's algorithm, for example, allows you to create a suffix tree online in O(n) time complexity.

The difference is very simple. A suffix tree has less "dummy" nodes than the suffix trie. These dummy nodes are single characters that increase the lookup operation at the tree

Trie's nodes have links to shorter context, 'Tree' does not have it. If Tree's nodes get link to shorter context then it turns to Trie ;o)

A Suffix Tree for a given text is a compressed trie for all suffixes of the given text.

Ref: https://www.geeksforgeeks.org/pattern-searching-using-suffix-tree/

I'll give you snippets to make your understanding clearer. Disclaimer: I'm not an expert and know these DS from coding interview preparations.

At first, as was said above: suffix trie is a structure made up of hash tables (simplest variant) where we store all possible variants. So, we can search substrings if needed. Ex: 'abc'.

{'a': True,
'a': {'b': True},
'a': {'b': {'c': True}},
'b': True,
'b': {'c': True},
'c': True}

And Trie is when we store full strings to check if they're present. Ex: {'t': {'h': {'i': {'s': {'*': 'this'}}}}, 'y': {'o': {'*': 'yo'}}

You can check for further explanation question on Leetcode: Implement Trie (Prefix Tree). Link: https://leetcode.com/problems/implement-trie-prefix-tree/

I hope this example of suffix trees using js can help

class SuffixTrie {
constructor(string) {
this.root = {};
this.endSymbol = '*';
this.populateSuffixTrieFrom(string);
}


// O(n^2) time | O(n^2) space
populateSuffixTrieFrom(string) {
for (let i = 0; i < string.length; i++)
this.insertSubStringStartingAt(i, string);
}


insertSubStringStartingAt(i, string) {
let node = this.root;
for (let j = i; j < string.length; j++) {
const letter = string[j];
if (!node.hasOwnProperty(letter)) node[letter] = {};
node = node[letter];
}


node[this.endSymbol] = true;
}


// O(m) time | O(1) space
contains(string) {
let node = this.root;
for (let letter of string) {
if (!node.hasOwnProperty(letter)) return false;
node = node[letter];
}
return node.hasOwnProperty(this.endSymbol);
}
}