LeetCode 226 ·
Easy
Invert Binary Tree
Invert a binary tree (swap every left and right child).
Try it
Step through the core mechanic. The simulator below runs the recursion shape this problem is built on.
Walk the pattern
No dedicated step-through for this one yet. The shape is Recursion — its pattern page has the interactive walkthrough, the reference implementation, and a five-problem progression that this problem sits inside.
The approach
Recurse: swap the children, then invert each subtree. Base case is a null node. Three lines once you trust the recursion.
| Aspect | Value |
|---|---|
| Pattern | Recursion |
| Recognise it by | Mirror a tree left-to-right. |
| Time complexity | O(n) |
| Space complexity | O(h) |
| Difficulty | Easy |
Who asks it
Companies known to ask this problem, from public LeetCode company-tag aggregations. A signal of where to expect it, not a guarantee.