July 11, 2023

Trie, also known as a prefix tree, is a tree-based data structure that allows efficient string searching and retrieval operations. Mastering trie implementation is crucial for tackling blind 75 Leetcode questions, where problem statements might not explicitly mention the need for a trie but can be efficiently solved using this data structure.

A trie is a tree-based data structure, often used to efficiently store and retrieve strings. It is composed of nodes, where each node represents a character. The root node represents an empty string, and each subsequent level in the trie represents the next character in a string. To efficiently search a string, we traverse the trie from the root to a leaf node, following the path that matches the characters of the string. This makes trie an excellent choice for problems involving string searching, auto-completion, and dictionary implementations.

Implementing a trie involves creating a class or struct representing the trie node. Each node can contain an array or hashmap to store child nodes, which can be accessed based on the corresponding character values. Additionally, each node might contain an attribute to indicate the end of a string. Here is a simple example of trie implementation:

```python

class TrieNode:

def __init__(self):

self.children = [None] * 26

self.is_end_of_word = False

class Trie:

def __init__(self):

self.root = TrieNode()

def insert(self, word):

node = self.root

for char in word:

index = ord(char) - ord('a')

if not node.children[index]:

node.children[index] = TrieNode()

node = node.children[index]

node.is_end_of_word = True

def search(self, word):

node = self.root

for char in word:

index = ord(char) - ord('a')

if not node.children[index]:

return False

node = node.children[index]

return node.is_end_of_word

```

- 1. Add and Search Word - Data Structure Design
- 2. Implement Trie (Prefix Tree)
- 3. Word Search II
- 4. Number of Matching Subsequences
- 5. Concatenated Words
- 6. Design Search Autocomplete System
- 7. Stream of Characters
- 8. Short Encoding of Words

- Q: Can trie be used only for characters or strings?
- A: No, trie can be used for any type of data, not just characters or strings. Each node in the trie can hold a reference to the next level based on the data type being used.
- Q: Are there any trie-specific operations other than insertion and search?
- A: Yes, trie can be used for various operations like prefix matching, auto-completion, and pattern searching. It can also be extended for applications like spell checking and recommendation systems.
- Q: How does a trie compare in terms of time complexity with other data structures?
- A: Trie provides efficient operations for searching and retrieval, with a time complexity of O(L), where L is the length of the string being processed. This makes it suitable for problems involving a large number of strings and searching based on prefixes.

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