What Is Trie Data Structure in C?


Heather Bennett

A Trie, also known as a prefix tree, is a tree-based data structure that is widely used in computer science and information retrieval. It is particularly efficient for searching and storing strings. In this article, we will explore the Trie data structure in C.

What is a Trie?

A Trie is a tree-like data structure that stores a collection of strings. Each node in the Trie represents a character, and the edges between the nodes represent the next possible characters.

The root of the Trie represents an empty string, and each path from the root to a leaf node represents a valid string.

Why use a Trie?

Tries are commonly used when efficient string searching or prefix matching is required. Unlike other data structures like arrays or linked lists, Tries have fast lookup times for searching words or prefixes.

Key features of Tries:

  • Prefix Searching: Tries are particularly efficient when it comes to prefix searching. With Tries, we can easily find all words that start with a given prefix.
  • Time Complexity: The time complexity for searching in Tries is O(m), where m is the length of the search word. This makes tries extremely efficient for searching words.
  • Space Efficiency: While tries offer fast search times, they can consume more memory compared to other data structures due to their hierarchical nature.

Trie implementation in C

To implement a Trie in C, we can define a node structure that contains an array of pointers to child nodes representing each character of the alphabet. Additionally, each node can have an ‘end_of_word’ flag indicating whether it marks the end of a word.

#define ALPHABET_SIZE 26

struct TrieNode {
bool end_of_word;
struct TrieNode* children[ALPHABET_SIZE];

Now, let’s look at the basic operations we can perform on a Trie:


To insert a word into a Trie, we start from the root and follow the path corresponding to each character in the word. If a node for a character doesn’t exist, we create a new node and attach it as a child of the current node.

After inserting all characters, we mark the last node as an end_of_word.


Searching in a Trie is similar to insertion. We start from the root and follow the path corresponding to each character in the search word.

If at any point, we encounter a NULL pointer or reach the end of the search word without finding all characters, it means that the word is not present in the Trie.


Deleting a word from a Trie is slightly more complex than insertion or searching. We traverse through each character of the word and remove nodes that are no longer used (i.e., have no child nodes) while backtracking towards the root.


In conclusion, Tries are powerful data structures for efficient string searching or prefix matching operations. Despite consuming more memory compared to other data structures, Tries provide fast search times and are widely used in applications like spell checkers, autocomplete systems, and IP routing tables.

By understanding how Tries work and implementing them in C using appropriate data structures and algorithms, you can harness their power for various applications.

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