Java - How to Create a Binary Search Tree
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Join For Freethis article represents the high level concept and code samples which could be used to create a binary search tree in java. please feel free to comment/suggest if i missed to mention one or more important points. also, sorry for the typos.
following are the key points described later in this article:
- what is a binary search tree?
- what are different kind of traversals?
- code samples
what is a binary search tree?
a binary search tree is a binary tree in which every node contains a key that satisfies following criteria:
- the key in left child is less than the key in the parent node
- the key in the right child is more than the parent node
- the left and right child are again binary search trees.
following diagram represents a binary search tree:
what are different kind of traversals?
following are three different kind of traversals:
- preorder traversal : in preorder traversal, the node is visted first and then, left and right sub-trees.
- inorder traversal : in inorder traversal, the node is visited between left and right sub-tree.
- postorder traversal : in postorder traversal, the node is visited after left and right subtrees.
code sample – how to create a binary search tree
if the numbers such as {20, 15, 200, 25, -5, 0, 100, 20, 12, 126, 1000, -150} are to be stored in a binarytree (represented by code below), following would get printed using different kind of traversal mechanism:
//preorder traversal 20, 15, -5, -150, 0, 12, 200, 25, 20, 100, 126, 1000 // inorder traversal -150, -5, 0, 12, 15, 20, 20, 25, 100, 126, 200, 1000 //postorder traversal -150, 12, 0, -5, 15, 20, 126, 100, 25, 1000, 200, 20
following is the code for creating binary tree that uses following binarytree class and traversals:
binarytree tree = new binarytree( 20 ); int[] nums = {15, 200, 25, -5, 0, 100, 20, 12, 126, 1000, -150}; for(int i : nums ) { tree.addnode( i ); } tree.traversepreorder(); tree.traverseinorder(); tree.traversepostorder();
following is the code for binarytree class:
public class binarytree { private int data; private binarytree left; private binarytree right; public binarytree(int num) { this.data = num; this.left = null; this.right = null; } // as a convention, if the key to be inserted is less than the key of root node, then key is inserted in // left sub-tree; if key is greater, it is inserted in right sub-tree. if it is equal, as a convention, it // is inserted in right sub-tree public void addnode(int num) { if (num < this.data) { if (this.left != null) { this.left.addnode(num); } else { this.left = new binarytree(num); } } else { if (this.right != null) { this.right.addnode(num); } else { this.right = new binarytree(num); } } } // visit the node first, then left and right sub-trees public void traversepreorder() { system.out.println( this.data ); if( this.left != null ) { this.left.traversepreorder(); } if( this.right != null ) { this.right.traversepreorder(); } } // visit left sub-tree, then node and then, right sub-tree public void traverseinorder() { if( this.left != null ) { this.left.traverseinorder(); } system.out.println( this.data ); if( this.right != null ) { this.right.traverseinorder(); } } // visit left sub-tree, then right sub-tree and then the node public void traversepostorder() { if( this.left != null ) { this.left.traversepostorder(); } if( this.right != null ) { this.right.traversepostorder(); } system.out.println( this.data ); } }
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