This is a Python program to find the sum of all nodes in a tree.

The program creates a tree and finds the sum of all nodes in the tree.

1. Create a class Tree with instance variables key and children.

2. Define methods set_root, add, sum_nodes and search.

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

4. The method add appends a node to the list children.

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

6. The method sum_nodes finds the sum of all nodes in the tree.

Here is the source code of a Python program to find the sum of all nodes in a tree. The program output is shown below.

class Tree: def __init__(self, data=None): self.key = data self.children = [] def set_root(self, data): self.key = data def add(self, node): self.children.append(node) def search(self, key): if self.key == key: return self for child in self.children: temp = child.search(key) if temp is not None: return temp return None def sum_nodes(self): summation = self.key for child in self.children: summation = summation + child.sum_nodes() return summation tree = None print('Menu (this assumes no duplicate keys)') print('add <data> at root') print('add <data> below <data>') print('sum') print('quit') while True: do = input('What would you like to do? ').split() operation = do[0].strip().lower() if operation == 'add': data = int(do[1]) new_node = Tree(data) suboperation = do[2].strip().lower() if suboperation == 'at': tree = new_node elif suboperation == 'below': position = do[3].strip().lower() key = int(position) ref_node = None if tree is not None: ref_node = tree.search(key) if ref_node is None: print('No such key.') continue ref_node.add(new_node) elif operation == 'sum': if tree is None: print('Tree is empty.') else: summation = tree.sum_nodes() print('Sum of all nodes: {}'.format(summation)) 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 sum_nodes is called on the tree to calculate the sum of all nodes in the tree.

Case 1: Menu (this assumes no duplicate keys) add <data> at root add <data> below <data> sum quit What would you like to do? sum Tree is empty. What would you like to do? add 3 at root What would you like to do? sum Sum of all nodes: 3 What would you like to do? add 4 below 3 What would you like to do? sum Sum of all nodes: 7 What would you like to do? add 5 below 3 What would you like to do? add 10 below 4 What would you like to do? sum Sum of all nodes: 22 What would you like to do? quit Case 2: Menu (this assumes no duplicate keys) add <data> at root add <data> below <data> sum quit What would you like to do? add 1 at root What would you like to do? add 2 below 1 What would you like to do? add 3 below 1 What would you like to do? add 4 below 1 What would you like to do? add 5 below 2 What would you like to do? add 6 below 3 What would you like to do? add 7 below 4 What would you like to do? sum Sum of all nodes: 28 What would you like to do? quit

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