# Which Data Structure Is Used for BST?

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Angela Bailey

A Binary Search Tree (BST) is a fundamental data structure used in computer science to efficiently store and retrieve elements in a sorted order. It provides quick access to its elements and is widely used in various applications such as searching, sorting, and data compression. In this article, we will explore the data structure used for implementing a BST.

## The Node Structure

At the heart of a BST lies its node structure. Each node in the tree contains three essential components:

• Key: The value of the node that determines its position in the tree.
• Left Child: A pointer to the left child node, which has a smaller value than the current node.
• Right Child: A pointer to the right child node, which has a greater value than the current node.

The node structure can be defined using a class or struct in programming languages like C++, Java, or Python.

## Implementation

To implement a BST, we start with an empty root node and insert elements into the tree based on their values. When inserting a new element, we compare it with the current node’s key and traverse either to its left or right child accordingly. This process continues until we find an empty spot to place the new element.

The following steps outline how to insert an element into a BST:

1. If the tree is empty, create a new node with the given key as its value and make it the root of the tree.
2. If the key is less than (or equal to) the current node’s key, traverse to its left child. If the left child is empty, insert the new node here.

Otherwise, repeat this step for the left subtree.

3. If the key is greater than the current node’s key, traverse to its right child. If the right child is empty, insert the new node here. Otherwise, repeat this step for the right subtree.

It’s worth noting that a BST can store unique elements only. Duplicate elements are typically handled differently depending on the requirements of the application.

## Searching

The searching process in a BST involves comparing a Target value with each node’s key until a match is found or we reach a null pointer. The search algorithm follows these steps:

1. If the tree is empty, return null as there are no elements to search.
2. If the Target value matches the current node’s key, return the node.
3. If the Target value is less than (or equal to) the current node’s key, traverse to its left child and repeat from step 2.
4. If the Target value is greater than the current node’s key, traverse to its right child and repeat from step 2.
5. If we reach a null pointer, it means that the Target value does not exist in the tree. Return null or an appropriate indication based on your implementation.

### Balanced vs. Unbalanced BSTs

A balanced BST ensures optimal performance by minimizing search time. It achieves this by maintaining roughly equal numbers of nodes in both subtrees of each node. On average, searching and insertion operations in a balanced BST have a time complexity of O(log n), where n is the number of elements.

On the other hand, an unbalanced BST may degenerate into a linked list if elements are inserted in a sorted or nearly sorted order. This results in degraded performance, with search and insertion operations having a worst-case time complexity of O(n), where n is the number of elements.

### Conclusion

In conclusion, a Binary Search Tree (BST) is implemented using nodes that contain key values and pointers to left and right child nodes. Insertion and searching operations are performed by comparing values and traversing the tree accordingly. Keeping the tree balanced ensures optimal performance, while an unbalanced tree can lead to degraded efficiency.

Understanding the data structure used for implementing a BST is crucial for utilizing its advantages and optimizing algorithms that rely on it.