Python Program for Tree Traversals

This program demonstrates three types of binary tree traversals: in-order, pre-order, and post-order. These traversal methods are implemented recursively to visit each node in the specific order required by each traversal type.

class TreeNode:
    """A node in a binary tree."""
    def __init__(self, value):
        """
        Initialize a tree node with a value.
        
        :param value: int, the integer value of the node
        """
        self.val = value
        self.left = None
        self.right = None

def inorderTraversal(root):
    """
    Perform in-order traversal of the binary tree.

    :param root: TreeNode, the root of the binary tree
    :return: List[int], the elements in in-order
    """
    if root is None:
        return []
    return inorderTraversal(root.left) + [root.val] + inorderTraversal(root.right)

def preorderTraversal(root):
    """
    Perform pre-order traversal of the binary tree.

    :param root: TreeNode, the root of the binary tree
    :return: List[int], the elements in pre-order
    """
    if root is None:
        return []
    return [root.val] + preorderTraversal(root.left) + preorderTraversal(root.right)

def postorderTraversal(root):
    """
    Perform post-order traversal of the binary tree.

    :param root: TreeNode, the root of the binary tree
    :return: List[int], the elements in post-order
    """
    if root is None:
        return []
    return postorderTraversal(root.left) + postorderTraversal(root.right) + [root.val]

# Example Usage
if __name__ == "__main__":
    # Construct a simple binary tree
    root = TreeNode(1)
    root.left = TreeNode(2)
    root.right = TreeNode(3)
    root.left.left = TreeNode(4)
    root.left.right = TreeNode(5)

    # In-order traversal
    print("In-order traversal:", inorderTraversal(root))
    # Pre-order traversal
    print("Pre-order traversal:", preorderTraversal(root))
    # Post-order traversal
    print("Post-order traversal:", postorderTraversal(root))

The program defines a TreeNode class to represent the nodes of the tree and three functions to perform each type of traversal. Each traversal function recursively visits nodes according to the traversal order: in-order, pre-order, or post-order. The results are returned as lists of values, demonstrating the order in which nodes are visited.