# Top view of binary tree using recursion in scala

Scala program for Top view of binary tree using recursion. Here problem description and explanation.

``````/*
Scala program for
Top view of binary tree using dfs
*/
// Binary Tree Node
class TreeNode(var data: Int,
var left: TreeNode,
var right: TreeNode)
{
def this(data: Int)
{
// Set node value
this(data, null, null);
}
}
class BinaryTree(var root: TreeNode,
var level: Int)
{
def this()
{
this(null, 0);
}
// Print left side top nodes including root
def printleftSide(node: TreeNode, depth: Int): Unit = {
if (node != null)
{
if (this.level < depth)
{
// Print the resultant node
print("  " + node.data);
this.level = depth;
}
// Recursively
// Visit left subtree
printleftSide(node.left, depth + 1);
// Visit right subtree
printleftSide(node.right, depth - 1);
}
}
// Print right side top nodes
def printRightSide(node: TreeNode, depth: Int): Unit = {
if (node != null)
{
if (this.level < depth)
{
// Print the resultant node
print("  " + node.data);
this.level = depth;
}
// Recursively
// First visit right subtree
printRightSide(node.right, depth + 1);
// Then
// Visit left subtree
printRightSide(node.left, depth - 1);
}
}
// This is handle the request of printing top view
def topView(): Unit = {
this.level = -1;
printleftSide(this.root, 0);
this.level = 0;
printRightSide(this.root, 0);
}
}
object Main
{
def main(args: Array[String]): Unit = {
// Create new tree
var tree: BinaryTree = new BinaryTree();
/*
Make A Binary Tree
-----------------------
1
/   \
2     3
/     / \
4     5   6
/       \
7         8
\
9
\
10
*/
// Construct binary tree
tree.root = new TreeNode(1);
tree.root.left = new TreeNode(2);
tree.root.right = new TreeNode(3);
tree.root.right.right = new TreeNode(6);
tree.root.right.left = new TreeNode(5);
tree.root.left.left = new TreeNode(4);
tree.root.left.left.left = new TreeNode(7);
tree.root.right.left.right = new TreeNode(8);
tree.root.right.left.right.right = new TreeNode(9);
tree.root.right.left.right.right.right = new TreeNode(10);
// Display top view
tree.topView();
}
}``````

Output

``  1  2  4  7  3  6  10``

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