Please include a summary of the changes and the related issue(s) this pull request addresses. Include any relevant context or background information.
The problem asks whether two binary trees are flip equivalent. Two trees are flip equivalent if they are the same when flipped at any node, meaning that at any node, we can swap the left and right subtrees.
My first thought is that we need to check the values of the nodes in a recursive manner. At each node, we either check if both left and right subtrees are the same without flipping, or we check if they are the same with flipping (i.e., left subtree of one tree corresponds to the right subtree of the other and vice versa).
Fixes: #45 (replace with the issue number, if applicable)
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Use [ ] to represent an unchecked box.❌
Type of Change
[ ] Question Added
[x] Solution Added
[ ] Other (please specify):
How to Test
We can solve this using recursion. At each step:
If both nodes are NULL, they are trivially equivalent.
If only one of them is NULL or their values are different, they cannot be flip equivalent.
Recursively check the following two possibilities:
The left subtree of the first tree is flip equivalent to the left subtree of the second tree, and the right subtree of the first tree is flip equivalent to the right subtree of the second tree.
The left subtree of the first tree is flip equivalent to the right subtree of the second tree, and the right subtree of the first tree is flip equivalent to the left subtree of the second tree.
By considering both cases, we ensure that we account for potential flips at every node.
Checklist
[x] I have performed a self-review of my code.
[ ] I have commented my code, particularly in hard-to-understand areas.
[ ] I have made corresponding changes to the documentation (if applicable).
[x] My changes generate no new warnings.
[ ] I have added tests to cover my changes (if applicable).
[x] All new and existing tests pass.
Additional Notes
Complexity
Time complexity: $$O(n)$$
Space complexity: $$O(h)$$
Please add any other information that is relevant to this pull request, including potential risks, alternative solutions considered, or future improvements.
Problem of the Day (October 24)
Description
Please include a summary of the changes and the related issue(s) this pull request addresses. Include any relevant context or background information. The problem asks whether two binary trees are flip equivalent. Two trees are flip equivalent if they are the same when flipped at any node, meaning that at any node, we can swap the left and right subtrees. My first thought is that we need to check the values of the nodes in a recursive manner. At each node, we either check if both left and right subtrees are the same without flipping, or we check if they are the same with flipping (i.e., left subtree of one tree corresponds to the right subtree of the other and vice versa).
Fixes: #45 (replace with the issue number, if applicable)
Use [x] to represent a checked (ticked) box.✅ Use [ ] to represent an unchecked box.❌
Type of Change
How to Test
We can solve this using recursion. At each step:
If only one of them is NULL or their values are different, they cannot be flip equivalent.
Recursively check the following two possibilities:
By considering both cases, we ensure that we account for potential flips at every node.
Checklist
Additional Notes
Complexity Time complexity: $$O(n)$$ Space complexity: $$O(h)$$
Please add any other information that is relevant to this pull request, including potential risks, alternative solutions considered, or future improvements.