What Is Trie in Data Structure?


Scott Campbell

A trie, also known as a prefix tree, is a specialized tree-based data structure that is commonly used to efficiently store and retrieve strings. It is particularly useful in applications that involve searching for words or prefixes in large collections of text data.

Structure of a Trie:
In a trie, each node represents a character or a partial string. The root node represents an empty string, and the child nodes represent the characters that can follow the current node’s string. Each node can have multiple child nodes, with each child representing one possible character.

Why Use a Trie?
One of the main advantages of using a trie is its efficiency when it comes to searching for words or prefixes. Unlike other data structures like arrays or hash tables, which require linear time to search for a word, a trie can perform this operation in constant time. This makes it an ideal choice for applications where fast lookup times are crucial.

Operations on Tries:


To insert a word into a trie, we start from the root node and iteratively add child nodes for each character in the word. If a node already exists for the current character, we move to that node; otherwise, we create a new node and link it to its parent node.


Searching for a word in a trie involves traversing the tree starting from the root node. We compare each character with the corresponding child nodes until we reach either the end of the word or encounter an invalid path. If we successfully traverse all characters of the word and reach an end-of-word marker flag at some node, it means that the word exists in the trie.


Deleting a word from a trie requires two steps: marking the end-of-word flag as false and removing any unnecessary nodes. To remove unnecessary nodes, we recursively check if a node has no children and is not the end of another word. If so, we can safely delete that node and continue this process until we reach a node with children or an end-of-word flag.

Applications of Tries:

  • Auto-complete: Tries are commonly used in auto-complete functionality, where suggestions are provided based on partially entered words. The trie structure allows for efficient retrieval of all possible completions.
  • Spell Checking: Tries can be used to build spell-checking systems.

    By storing all valid words in a trie, it becomes easy to check if a given word is misspelled.

  • Word Games: Tries are also useful in word games like Scrabble, where players need to find valid words from a given set of letters. Using a trie, it becomes straightforward to check the validity of potential words.
  • IP Routing: In computer networks, tries are used for efficient IP address lookups. By storing network prefixes in a trie structure, routers can quickly determine the next hop for an incoming packet.


Tries provide an efficient way to store and search for strings or prefixes. With their fast lookup times and flexibility, they find applications in various domains such as text processing, spelling correction, network routing, and more. Understanding tries and their operations can greatly enhance your problem-solving skills when dealing with string-related tasks.

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