DSA · Theory

Transform a BST to greater sum tree

Theory

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Transform a BST to greater sum tree

Don’t start Transform a BST to greater sum tree with jargon. Start with folder on disk. That is the whole point.

Transform a BST to greater sum tree order: meaning → left < root < right → one limit. Dumping ten features helps nobody.

Without Transform a BST to greater sum tree, a file explorer gets messy and folder on disk is hard to trust.

Transform a BST to greater sum tree shows up in a file explorer. Name folder on disk, not “a real-world scenario”.

Don’t do this with Transform a BST to greater sum tree: unbalanced BST becoming a list. Interviewers spot it in ten seconds.

After Transform a BST to greater sum tree, Kabir should still remember unbalanced BST becoming a list.

Close Transform a BST to greater sum tree with: “If I skip it, folder on disk goes wrong like this: unbalanced BST becoming a list.”

Diagram

Exam tip

For Transform a BST to greater sum tree: definition + a file explorer + one failure.

Example

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

def insert(root, val):
    if root is None:
        return Node(val)
    if val < root.val:
        root.left = insert(root.left, val)
    elif val > root.val:
        root.right = insert(root.right, val)
    return root

root = None
for v in [5, 2, 7, 1]:
    root = insert(root, v)
print(root.val, root.left.val, root.right.val)

Transform a BST to greater sum tree — bST invariant: left < node < right — enables log-time search when balanced.

Short notes

DefTransform a BST to greater sum tree — Kabir uses it for folder on disk in a file explorer.
RuleTransform a BST to greater sum tree → left < root < right.
RememberTransform a BST to greater sum tree + a dry-run table (a file explorer).
UseTransform a BST to greater sum tree in a file explorer (folder on disk).
TrapTransform a BST to greater sum tree — unbalanced BST becoming a list.
ExTransform a BST to greater sum tree → folder on disk.

class Node: def __init__(self, val): self.val = val self.left = None self.right = None def insert(root, val): if root is None: return Node(val) if val < root.val: root.left = insert(root.left, val) elif val > root.val: root.right = insert(root.right, val) return root root = None for v in [5, 2, 7, 1]: root = insert(root, v) print(root.val, root.left.val, root.right.val)

Transform a BST to greater sum tree

Example

Short notes

Questions

Transform a BST to greater sum tree

Example

Short notes

Questions