【Arai60】24問目 108_Convert Sorted Array to Binary Search Tree #24
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
hayashi-ay
reviewed
Mar 14, 2024
| root = TreeNode(nums[mid]) | ||
| queue = deque([(root, (0, mid - 1), (mid + 1, len(nums) - 1))]) | ||
| while queue: | ||
| node, left_range, right_range = queue.popleft() |
There was a problem hiding this comment.
parentとかでもいいかも。
Suggested change
| node, left_range, right_range = queue.popleft() | |
| parent, left_range, right_range = queue.popleft() |
There was a problem hiding this comment.
BFSの方はparentの方が分かりやすいですね。
| queue = deque([(root, (0, mid - 1), (mid + 1, len(nums) - 1))]) | ||
| while queue: | ||
| node, left_range, right_range = queue.popleft() | ||
| if left_range[0] <= left_range[1]: |
There was a problem hiding this comment.
関数に切り出すとかしても良いかも。うまく切り出せるかは試してないですが。
| node.right = helper(mid + 1, right) | ||
| return node | ||
|
|
||
| return helper(0, len(nums) - 1) |
| class Solution: | ||
| def sortedArrayToBST(self, nums: List[int]) -> Optional[TreeNode]: | ||
| mid = (len(nums) - 1) // 2 | ||
| root = TreeNode(nums[mid]) |
There was a problem hiding this comment.
LeetCodeの制約ではlen(nums) >= 1が保証されてますが、空配列だとIndexErrorになりますね。
| def helper(left, right): | ||
| if left > right: | ||
| return None | ||
| mid = (left + right) // 2 |
There was a problem hiding this comment.
コードからは意識してるか分からなかったので念の為共有です。範囲に含まれる要素が偶数のときに真ん中が存在しないのでmidの選択により左と右のどちらをrootにするかが決まりますね。
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
問題
https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/