105. Construct Binary Tree from Preorder and Inorder Traversal#28
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105. Construct Binary Tree from Preorder and Inorder Traversal#28hemispherium wants to merge 1 commit into
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nodchip
reviewed
Apr 21, 2026
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| TreeNode* build( | ||
| const vector<int>& preorder, | ||
| int preL, |
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lowerCamel と lower_snake が混ざっている点に違和感を感じました。 lower_snake に統一するとよいと思います。
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そうですね、統一するほうがいいと思います。
| */ | ||
| class Solution { | ||
| public: | ||
| unordered_map<int, int> inorder_val_to_index; |
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こちらのコメントをご参照ください。
5ky7/arai60#22 (comment)
quinn-sasha
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Apr 21, 2026
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| if (it - inorder.begin() != in_right) { | ||
| tree->right = new TreeNode(preorder[pre_left + it - (inorder.begin() + in_left) + 1]); |
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事前にイテレータから添字に変換しておくと、ここら辺のコードが読みやすくなると思います。
条件式やコンストラクタの中で変換すると少し難しくなると思います
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コメントありがとうございます。そうですね、条件式やコンストラクタの中で変換するのは煩雑になってしまいそうです。
quinn-sasha
reviewed
Apr 21, 2026
| const vector<int>& preorder, | ||
| int preL, | ||
| int preR, | ||
| int inL |
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この preR, inL など添字の役割が少し複雑だと感じました。
preorder は単に左から右にインクリメントする添字があれば十分なのですが、preorder の範囲を管理しているのがやらなくても良いことをやっていることになり複雑になっていると思いました。
範囲を管理するのは inorder にした方が、直感的だと思います。
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この問題：https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/description/
次に解く問題：https://leetcode.com/problems/longest-increasing-subsequence/description/ (Paint Fenceがpremium限定のためスキップ。)