When it is required to display the nodes of a tree using the breadth first search traversal, a class is created, and it contains methods to set the root node, add elements to the tree, search for a specific element, perform ‘bfs’ (breadth first search) and so on. An instance of the class can be created to access and use these methods.
Below is a demonstration of the same −
class Tree_struct: def __init__(self, data=None): self.key = data self.children =  def set_root(self, data): self.key = data def add_node(self, node): self.children.append(node) def search_node(self, key): if self.key == key: return self for child in self.children: temp = child.search_node(key) if temp is not None: return temp return None def bfs_operation(self): queue = [self] while queue != : popped = queue.pop(0) for child in popped.children: queue.append(child) print(popped.key, end=' ') my_instance = None print('Menu (assume no duplicate keys)') print('add <data> at root') print('add <data> below <data>') print('bfs') print('quit') while True: my_input = input('What operation would you do ? ').split() operation = my_input.strip().lower() if operation == 'add': data = int(my_input) new_node = Tree_struct(data) suboperation = my_input.strip().lower() if suboperation == 'at': my_instance = new_node elif suboperation == 'below': position = my_input.strip().lower() key = int(position) ref_node = None if my_instance is not None: ref_node = my_instance.search_node(key) if ref_node is None: print('No such key') continue ref_node.add_node(new_node) elif operation == 'bfs': if my_instance is None: print('The tree is empty') else: print('Breadth First Search traversal is : ', end='') my_instance.bfs_operation() print() elif operation == 'quit': break
Menu (assume no duplicate keys) add <data> at root add <data> below <data> bfs quit What operation would you do ? add 6 at root What operation would you do ? add 4 below 6 What operation would you do ? add 9 below 4 What operation would you do ? bfs Breadth First Search traversal is : 6 4 9 What operation would you do ? quit
The ‘Tree_struct’ class with required attributes is created.
It has an ‘init’ function that is used to create an empty list.
A ‘set_root’ method is defined that helps set the root value of the binary tree.
It has an ‘add_node’ method that helps add elements to the tree.
A method named ‘search_elem’ is defined, that helps search for a specific element.
A method named ‘bfs_operation’ is defined, that helps perform breadth first search traversal on the tree.
An instance is created and assigned to ‘None’.
The user input is taken for the operation that needs to be performed.
Depending on the user’ choice, the operation is performed.
Relevant output is displayed on the console.