This is a Python program to perform depth-first search on a binary tree without using recursion.

The program creates a binary tree and presents a menu to the user to perform operations on the tree including depth-first search.

1. Create a class Stack to implement a stack.

2. The class Stack will have methods is_empty, push and pop.

3. Create a class BinaryTree with instance variables key, left and right.

4. Define methods set_root, insert_left, insert_right, preorder_depth_first and search.

5. The method set_root takes a key as argument and sets the variable key equal to it.

6. The methods insert_left and insert_right insert a node as the left and right child respectively.

7. The method search returns a node with a specified key.

8. The method preorder_depth_first displays a preorder DFS traversal of the tree.

9. The preorder traversal is implemented using a stack to avoid recursion.

Here is the source code of a Python program to perform depth-first search on a binary tree without using recursion. The program output is shown below.

class BinaryTree: def __init__(self, key=None): self.key = key self.left = None self.right = None def set_root(self, key): self.key = key def insert_left(self, new_node): self.left = new_node def insert_right(self, new_node): self.right = new_node def search(self, key): if self.key == key: return self if self.left is not None: temp = self.left.search(key) if temp is not None: return temp if self.right is not None: temp = self.right.search(key) return temp return None def preorder_depth_first(self): s = Stack() s.push(self) while (not s.is_empty()): node = s.pop() print(node.key, end=' ') if node.right is not None: s.push(node.right) if node.left is not None: s.push(node.left) class Stack: def __init__(self): self.items = [] def is_empty(self): return self.items == [] def push(self, data): self.items.append(data) def pop(self): return self.items.pop() btree = BinaryTree() print('Menu (this assumes no duplicate keys)') print('insert <data> at root') print('insert <data> left of <data>') print('insert <data> right of <data>') print('dfs') print('quit') while True: do = input('What would you like to do? ').split() operation = do[0].strip().lower() if operation == 'insert': data = int(do[1]) new_node = BinaryTree(data) suboperation = do[2].strip().lower() if suboperation == 'at': btree = new_node else: position = do[4].strip().lower() key = int(position) ref_node = None if btree is not None: ref_node = btree.search(key) if ref_node is None: print('No such key.') continue if suboperation == 'left': ref_node.insert_left(new_node) elif suboperation == 'right': ref_node.insert_right(new_node) elif operation == 'dfs': print('pre-order dfs traversal: ', end='') if btree is not None: btree.preorder_depth_first() print() elif operation == 'quit': break

1. A variable is created to store the binary tree.

2. The user is presented with a menu to perform operations on the tree.

3. The corresponding methods are called to perform each operation.

4. The method preorder_depth_first is called to display a DFS pre-order traversal of the tree.

Case 1: Menu (this assumes no duplicate keys) insert <data> at root insert <data> left of <data> insert <data> right of <data> dfs quit What would you like to do? insert 1 at root What would you like to do? insert 2 left of 1 What would you like to do? insert 3 right of 1 What would you like to do? insert 4 right of 2 What would you like to do? insert 5 left of 4 What would you like to do? dfs pre-order dfs traversal: 1 2 4 5 3 What would you like to do? quit Case 2: Menu (this assumes no duplicate keys) insert <data> at root insert <data> left of <data> insert <data> right of <data> dfs quit What would you like to do? insert 3 at root What would you like to do? insert 6 left of 3 What would you like to do? insert 7 right of 3 What would you like to do? insert 8 left of 7 What would you like to do? insert 10 right of 7 What would you like to do? dfs pre-order dfs traversal: 3 6 7 8 10 What would you like to do? quit

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