Foldable Binary Tree

April 6, 2023

Check if a Tree is foldable or Not

Here, in this page we will write a Java program to check whether the given binary tree is foldable or not. A Tree is said to be foldable if its left and right counter part can be made to overlap with each other .

Foldable Binary Tree

Algorithm :

If tree is empty, then return true.
Convert the left subtree to its mirror image mirror(root->left);
Check if the structure of left subtree and right subtree is same and store the result. res = isStructSame(root->left, root->right);
isStructSame() recursively compares structures of two subtrees and returns true if structures are same
Revert the changes made in step 2 to get the original tree. mirror(root->left);
Return result res stored in step 2.

Find size of the Binary tree

Find the height of binary tree

Find maximum in binary tree

Check for Children-Sum in Binary Tree

check whether tree is Symmetric

Code in Java for Level Order Traversal Line by Line

Run

class Node {
    int data;
    Node left, right;

    public Node(int item) {
        data = item;
        left = right = null;
    }
    public Node() {
        data = 0;
        left = right = null;
    }
}

// Binary tree Class
class BTree {

    static Node root;
    static boolean isFoldableTree(Node node) {
        if (node == null) {
            return true;
        }
        return isFoldable(node.left, node.right);
    }

    static boolean isFoldable(Node nodeLeft, Node nodeRight) {

        //Check both left and right node is null, if yes then that is fine, return true.
        if (nodeLeft == null && nodeRight == null) {
            return true;
        }
        //If one is present and other is null, return false.
        if (nodeLeft == null || nodeRight == null) {
            return false;
        }
        // The most Important step is -> when you are Checking if it is structurally a mirror image , 
        // Send the left child of left subtree and right child of right subtree //   together. Similarly,
        // send the right child of left subtree and left child of right subtree. 
        boolean left = isFoldable(nodeLeft.left, nodeRight.right);
        boolean right = isFoldable(nodeLeft.right, nodeRight.left);

        return (left && right);
    }
}
public class Main{



    public static void main(String[] args) {
        BTree tree = new BTree();
        tree.root = new Node(1);
        tree.root.left = new Node(5);
        tree.root.right = new Node(4);
        tree.root.left.left = new Node(9);
        tree.root.left.right = new Node(7);
        tree.root.right.left = new Node(10);
        tree.root.right.right = new Node(13);
        System.out.println(" The Given Tree is Foldable :  " + tree.isFoldableTree(tree.root));

    }
}

Output

 The Given Tree is Foldable :  true

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