High BST Question 166 of 224

How do you recover a BST where exactly two nodes were swapped?

DSA interview set · Speak this in 60–90 seconds · Faridabad & Delhi NCR

01234

Index starts at 0. Scan once for max — O(n).

Inorder should be sorted

Why interviewers care about BST:

This is a process

question about BST.

Panels listen for order,

trade-offs, and what you would actually do on a DSA project - not buzzwords.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

Before you speak the answer, walk the interviewer through these steps:

1
Define it
Inorder should be sorted
2
find the one or
two inversions (first dip and last dip) and swap those node values.
3
Time is O(n) and
space is O(h) with recursion, or O(1) extra with Morris traversal.
4
Recreating the tree from
sorted keys would use extra arrays.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“Time is O(n) and space is O(h) with recursion, or O(1) extra with Morris travers”

Break into beats

TimeisOnandspace

Speaking order

2987408337471632900

Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

Inorder should be sorted find the one or two inversions (first dip and last dip) and swap those node values.