ivan-magda / ifmo-b-tree

IFMO - Advanced Data Structures

B-tree

B-tree is a self-balancing tree data structure that keeps data sorted and allows searches, sequential access, insertions, and deletions in logarithmic time. The B-tree is a generalization of a binary search tree in that a node can have more than two children. Unlike self-balancing binary search trees, the B-tree is optimized for systems that read and write large blocks of data. B-trees are a good example of a data structure for external memory. It is commonly used in databases and filesystems.

The Code:

• Searching:
  • value(for:) method searches for the given key and if it's in the tree, it returns the value associated with it, else it returns nil.
• Insertion:
  • The method insert(_:for:) does the insertion. After it has inserted a key, as the recursion goes up every node checks the number of keys in its child.
  • if a node has too many keys, its parent calls the split(child:atIndex:) method on it.
  • If the root has too many nodes after the insertion the tree calls the splitRoot() method.
• Deletion:
  • remove(_:) method removes the given key from the tree. After a key has been deleted, every node checks the number of keys in its child. If a child has less nodes than the order of the tree, it calls the fix(childWithTooFewKeys:atIndex:) method.
  • fix(childWithTooFewKeys:atIndex:) method decides which way to fix the child (by moving a key to it, or by merging it), then calls move(keyAtIndex:to:from:at:) or merge(child:atIndex:to:) method according to its choice.

Benchmarks Results:

• Charts

Helpful Links:

• Wikipedia
• geeksforgeeks
• cs.cornell.edu

LICENSE

This project is open-sourced software licensed under the MIT License.

See the LICENSE file for more information.