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Lowest Common Ancestor in a Binary Search Tree

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Lowest Common Ancestor in a Binary Search Tree

Lowest Common Ancestor in a Binary Search Tree is simple if you keep it on paper. Isha uses it for folder on disk in a file explorer.

For Lowest Common Ancestor in a Binary Search Tree, time vs memory is in play. Don’t blame it until you have traced folder on disk.

Skip Lowest Common Ancestor in a Binary Search Tree and unbalanced BST becoming a list shows up in a file explorer.

Use Lowest Common Ancestor in a Binary Search Tree when folder on disk must stay clear. If a simpler DSA step works, use that instead.

Don’t do this with Lowest Common Ancestor in a Binary Search Tree: unbalanced BST becoming a list. Interviewers spot it in ten seconds.

Place Lowest Common Ancestor in a Binary Search Tree next to nearby DSA work — left < root < right is the link.

Close Lowest Common Ancestor in a Binary Search Tree with: “If I skip it, folder on disk goes wrong like this: unbalanced BST becoming a list.”

Diagram

Exam tip

Board: folder on disk. Dry-run Lowest Common Ancestor in a Binary Search Tree. Name the trap: unbalanced BST becoming a list.

Example

def binary_search(arr, target):
    lo, hi = 0, len(arr) - 1
    while lo <= hi:
        mid = (lo + hi) // 2
        if arr[mid] == target:
            return mid
        if arr[mid] < target:
            lo = mid + 1
        else:
            hi = mid - 1
    return -1

print(binary_search([1, 3, 5, 7, 9], 7))

Lowest Common Ancestor in a Binary Search Tree — binary search halves a sorted array each step — O(log n).

Short notes

DefLowest Common Ancestor in a Binary Search Tree — Isha uses it for folder on disk in a file explorer.
RuleLowest Common Ancestor in a Binary Search Tree → left < root < right.
RememberLowest Common Ancestor in a Binary Search Tree + time vs memory (a file explorer).
UseLowest Common Ancestor in a Binary Search Tree in a file explorer (folder on disk).
TrapLowest Common Ancestor in a Binary Search Tree — unbalanced BST becoming a list.
ExLowest Common Ancestor in a Binary Search Tree → folder on disk.

def binary_search(arr, target): lo, hi = 0, len(arr) - 1 while lo <= hi: mid = (lo + hi) // 2 if arr[mid] == target: return mid if arr[mid] < target: lo = mid + 1 else: hi = mid - 1 return -1 print(binary_search([1, 3, 5, 7, 9], 7))

Lowest Common Ancestor in a Binary Search Tree

Example

Short notes

Questions

Lowest Common Ancestor in a Binary Search Tree

Example

Short notes

Questions