Build a Binary Tree - Python DSA

Create a fixed seven-node binary tree and render its shape.

Algorithm

The canonical tree is 4(2(1,3),6(5,7)), so this Python DSA implementation can be compared directly with the rest of the DSA track.

Basic Implementation

basic.py

class Node:
    def __init__(self, value, left=None, right=None):
        self.value = value
        self.left = left
        self.right = right

def render(node):
    if node is None:
        return "_"
    if node.left is None and node.right is None:
        return str(node.value)
    return f"{node.value}({render(node.left)},{render(node.right)})"

def sample_tree():
    n1 = Node(1)
    n3 = Node(3)
    n2 = Node(2, n1, n3)
    n5 = Node(5)
    n7 = Node(7)
    n6 = Node(6, n5, n7)
    return Node(4, n2, n6)

root = sample_tree()
print(render(root))

Complexity

Time: O(n)
Space: O(n)

Implementation notes

Render tree structure explicitly instead of printing node objects.
The replay highlights the node, traversal state, queue, path, or search cursor that changes at each step.

node links A node stores one value plus references to its left and right children.