DSA · Theory

Construct Tree from Given Inorder and Preorder Traversals

Theory

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Construct Tree from Given Inorder and Preorder Traversals

Construct Tree from Given Inorder and Preorder Traversals is a DSA topic. In plain words you use it for folder on disk in a file explorer. Don’t start with a slogan — start with that picture.

Smallest example: left < root < right. Type it, run it, and say what you see. If you can do that from memory, you know Construct Tree from Given Inorder and Preorder Traversals.

From the example next to this theory: Construct Tree from Given Inorder and Preorder Traversals — inorder walks left → node → right (sorted order for a BST).

Trap — unbalanced BST becoming a list. Fix that before you talk about advanced DSA.

Viva: what is Construct Tree from Given Inorder and Preorder Traversals? Then show left < root < right. Then name the trap.

Exam tip

What is Construct Tree from Given Inorder and Preorder Traversals? Show this: left < root < right. Trap: unbalanced BST becoming a list.

Example

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

def inorder(n):
    if not n:
        return []
    return inorder(n.left) + [n.val] + inorder(n.right)

root = Node(2, Node(1), Node(3))
print(inorder(root))

Construct Tree from Given Inorder and Preorder Traversals — inorder walks left → node → right (sorted order for a BST).

Short notes

DefConstruct Tree from Given Inorder and Preorder Traversals — folder on disk in a file explorer.
Ruleleft < root < right
Trapunbalanced BST becoming a list
Usea file explorer

class Node: def __init__(self, val, left=None, right=None): self.val, self.left, self.right = val, left, right def inorder(n): if not n: return [] return inorder(n.left) + [n.val] + inorder(n.right) root = Node(2, Node(1), Node(3)) print(inorder(root))

Construct Tree from Given Inorder and Preorder Traversals

Example

Short notes

Questions

Construct Tree from Given Inorder and Preorder Traversals

Example

Short notes

Questions