Java program to determine whether two trees are identical

by Online Tutorials Library July 22, 2022

Java program to determine whether two trees are identical

In this program, we need to check whether two trees are identical or not. For two trees to be identical, they have to satisfy two conditions:

Structure of both the trees should be the same.
Nodes present in one tree should be present in another tree.

Java program to determine whether two trees are identical

Above diagram contains three trees namely A, B, and C. Trees A and B are the identical as they are structurally same and values of all nodes are the same. However, trees A and C are structurally same but not identical as nodes are different in both the trees.

Algorithm

Define Node class which has three attributes namely: data left and right. Here, left represents the left child of the node and right represents the right child of the node.
When a node is created, data will pass to data attribute of the node and both left and right will be set to null.
Define another class which has an attribute root.
- Root represents the root node of the tree and initializes it to null.
areIdenticalTrees() will check whether two trees are identical or not:
- If root nodes of both the trees are null then, they are identical.
- If the root node of only one tree is null then, trees are not identical, return false.
- If root node of none of the tree is null, then check whether data of both the nodes are equal and then recursively check the left subtree and right subtree of one tree is identical to another or not.

Program:

  public class IdenticalTrees {          //Represent the node of the binary tree        public static class Node{          int data;          Node left;          Node right;            //Assign data to the new node, set left and right children to null          public Node(int data){            this.data = data;            this.left = null;            this.right = null;          }        }          //Represent the root of the binary tree        public Node root;          public IdenticalTrees(){          root = null;        }          //areIdenticalTrees() finds whether two trees are identical or not        public static boolean areIdenticalTrees(Node root1, Node root2) {              //Checks if both the trees are empty            if(root1 == null && root2 == null)                return true;              //Trees are not identical if root of only one tree is null thus, return false            if(root1 == null && root2 == null)                return true;              //If both trees are not empty, check whether the data of the nodes is equal            //Repeat the steps for left subtree and right subtree            if(root1 != null  && root2 != null) {                  return ((root1.data == root2.data) &&                        (areIdenticalTrees(root1.left, root2.left)) &&                        (areIdenticalTrees(root1.right, root2.right)));            }            return false;        }            public static void main(String[] args) {            //Adding nodes to the first binary tree          IdenticalTrees bt1 = new IdenticalTrees();          bt1.root = new Node(1);          bt1.root.left = new Node(2);          bt1.root.right = new Node(3);          bt1.root.left.left = new Node(4);          bt1.root.right.left = new Node(5);          bt1.root.right.right = new Node(6);            //Adding nodes to the second binary tree            IdenticalTrees bt2 = new IdenticalTrees();            bt2.root = new Node(1);            bt2.root.left = new Node(2);            bt2.root.right = new Node(3);            bt2.root.left.left = new Node(4);            bt2.root.right.left = new Node(5);            bt2.root.right.right = new Node(6);              //Displays whether both the trees are identical or not             if(areIdenticalTrees(bt1.root, bt2.root))               System.out.println(“Both the binary trees are identical”);           else               System.out.println(“Both the binary trees are not identical”);          }  }  

Output:

Both the binary trees are identical

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Java program to determine whether two trees are identical

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