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Diameter of a Binary Tree

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Diameter of a Binary Tree

Diameter of a Binary Tree sits in a file explorer. Dev’s job is folder on disk. Write that first.

Diameter of a Binary Tree on the board — left < root < right. Then say what folder on disk looks like after.

Diameter of a Binary Tree exists so Dev can keep folder on disk correct in a file explorer.

Dev ships Diameter of a Binary Tree in a file explorer. That is the use case worth saying.

Don’t do this with Diameter of a Binary Tree: unbalanced BST becoming a list. Interviewers spot it in ten seconds.

After Diameter of a Binary Tree, Dev should still remember unbalanced BST becoming a list.

Close Diameter of a Binary Tree with: “If I skip it, folder on disk goes wrong like this: unbalanced BST becoming a list.”

Exam tip

Board: folder on disk. Dry-run Diameter of a Binary Tree. Name the 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))

Diameter of a Binary Tree — inorder walks left → node → right (sorted order for a BST).

Short notes

DefDiameter of a Binary Tree — Dev uses it for folder on disk in a file explorer.
RuleDiameter of a Binary Tree → left < root < right.
RememberDiameter of a Binary Tree + Big-O (a file explorer).
UseDiameter of a Binary Tree in a file explorer (folder on disk).
TrapDiameter of a Binary Tree — unbalanced BST becoming a list.
ExDiameter of a Binary Tree → folder on disk.

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))

Diameter of a Binary Tree

Example

Short notes

Questions

Diameter of a Binary Tree

Example

Short notes

Questions