# Inorder traversal of binary tree using stack in swift

Swift program for Inorder traversal of binary tree using stack. Here problem description and explanation.

import Foundation
// Swift 4 program for
// Inorder traversal without recursion
// Using stack

// Binary Tree node
class TreeNode
{
var data: Int;
var left: TreeNode? ;
var right: TreeNode? ;
// Make a tree node
init(_ data: Int)
{
// Set node data
self.data = data;
self.left = nil;
self.right = nil;
}
}
class StackNode
{
var element: TreeNode? ;
var next: StackNode? ;
init(_ element: TreeNode? )
{
self.element = element;
self.next = nil;
}
}
// Stack Class
class MyStack
{
var top: StackNode? ;
var size: Int;
init()
{
self.top = nil;
self.size = 0;
}
// Add new element into stack
func push(_ element: TreeNode? )
{
// Create new node
let node: StackNode? = StackNode(element);
node!.next = self.top;
// new node is new top
self.top = node;
// Increase the size
self.size += 1;
}
// Remove top element of the stack
func pop()
{
if (self.top  != nil)
{
// next node is new top
self.top = self.top!.next;
// Reduce size
self.size -= 1;
}
}
// Returns the status of empty or non empty stacks
func isEmpty() -> Bool
{
if (self.size > 0 && self.top  != nil)
{
return false;
}
else
{
return true;
}
}
// Return top element of stack
func peek() -> TreeNode?
{
if (self.isEmpty())
{
return nil;
}
return self.top!.element;
}
}
class BinaryTree
{
var root: TreeNode? ;
init()
{
self.root = nil;
}
// Display Inorder view of binary tree
func inorder()
{
if (self.root  != nil)
{
// Make new stack
let s: MyStack? = MyStack();
var node: TreeNode? = self.root;
// Display tree element
while (!s!.isEmpty() || node  != nil)
{
if (node  != nil)
{
// Add current node
s!.push(node);
// Visit to left subtree
node = node!.left;
}
else
{
// When node is null
// Get stack top element
node = s!.peek();
// Display node value
print(node!.data, terminator: "  ");
// Remove top element of the stack
s!.pop();
// Visit to left subtree of current node
node = node!.right;
}
}
}
else
{
print("Empty Linked List");
}
}
static func main(_ args: [String])
{
// Create new tree
let tree: BinaryTree? = BinaryTree();
/*
Construct Binary Tree
-----------------------
15
/  \
24   54
/    /  \
35   62   13
*/
// Add tree nodes
tree!.root = TreeNode(15);
tree!.root!.left = TreeNode(24);
tree!.root!.right = TreeNode(54);
tree!.root!.right!.right = TreeNode(13);
tree!.root!.right!.left = TreeNode(62);
tree!.root!.left!.left = TreeNode(35);
// Display result
tree!.inorder();
}
}
BinaryTree.main([String]());

Output

35  24  15  62  54  13

## Comment

Please share your knowledge to improve code and content standard. Also submit your doubts, and test case. We improve by your feedback. We will try to resolve your query as soon as possible.

### New Comment

© 2022, kalkicode.com, All rights reserved