What Is TreeMap Data Structure?


Larry Thompson

A TreeMap is a data structure in computer science that stores key-value pairs in a sorted order. It is a variant of the binary search tree where each node is associated with a key and a value. The keys in the TreeMap are always sorted in ascending order.

How does it work?
The TreeMap uses a red-black tree as its underlying data structure to maintain the keys in sorted order. A red-black tree is a balanced binary search tree, meaning that it ensures that the height of the tree remains logarithmic, resulting in efficient operations.

When inserting a new key-value pair into the TreeMap, it follows these steps:

  1. Start from the root of the tree.
  2. If the tree is empty, create a new node with the given key and value.
  3. If the key already exists, update its value.
  4. If the key does not exist, find its correct position by comparing it with other keys.
  5. Insert the new node at its correct position while maintaining the sorted order.

Removing a key-value pair from the TreeMap involves these steps:

  1. Find the node with the given key.
  2. If found, remove it from the tree.

Advantages of using TreeMap:

  • Sorted Order: The TreeMap maintains keys in sorted order which makes it suitable for applications requiring sorted data.
  • Efficient Operations: As a balanced binary search tree, TreeMap provides efficient operations like insertion, deletion, and search with an average time complexity of O(log n).
  • Faster Key Lookup: Searching for keys in a TreeMap is faster compared to other data structures like arrays or linked lists since it uses a binary search algorithm.

Limitations of using TreeMap:

  • Slower than HashMap: TreeMap has a slower performance compared to HashMap for some operations like insertion and deletion, especially when dealing with large datasets.
  • No Constant Time Operations: Unlike HashMap, which provides constant time operations, TreeMap has logarithmic time complexity for most operations.


In summary, a TreeMap is a powerful data structure that maintains key-value pairs in sorted order. It offers efficient operations and faster key lookup compared to other data structures.

However, it may not be the best choice for scenarios where constant time operations or faster insertion and deletion are required. Consider the specific requirements of your application before deciding to use a TreeMap.

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