Invert Binary Tree
Mirror a binary tree by swapping the left and right child of every node.
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Lesson notes
Try it before you watch
Restate the problem in your own words, list the edge cases, and sketch a solution with its running time. Then play the video and compare.
Reveal the key idea
Swap the children of the current node and recurse into both subtrees (or do the same with a queue).
Pattern: Trees & tries. Most tree problems are a recursive question asked of the left subtree, the right subtree, and the root.
Complexity
| Measure | Bound |
|---|---|
| Time | O(n) |
| Extra space | O(h) |
Walkthroughs often start from a simpler approach first; aim to reach these bounds. New to Big-O? Read understanding algorithmic complexity.