105. Construct Binary Tree from Preorder and Inorder Traversal#29
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TakayaShirai wants to merge 1 commit intomainfrom
Open
105. Construct Binary Tree from Preorder and Inorder Traversal#29TakayaShirai wants to merge 1 commit intomainfrom
TakayaShirai wants to merge 1 commit intomainfrom
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mamo3gr
reviewed
Feb 23, 2026
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| int pickInorderRootIndex(List<int> inorder, int rootValue) { | ||
| var rootIndex = 0; | ||
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| for (var i = 0; i < inorder.length; i++) { | ||
| if (inorder[i] == rootValue) { | ||
| return i; | ||
| } | ||
| } | ||
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| throw Exception('inorder does not have the given rootValue.'); | ||
| } |
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ここは list.indexOf() を使うとどうでしょうか。
https://api.dart.dev/dart-core/List/indexOf.html
5ky7
reviewed
Feb 25, 2026
| ); | ||
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| root.left = leftTree; | ||
| root.right = rightTree; |
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Dartに詳しくないのですが，以下のようにかけるのならそちらの方がシンプルだと感じました．root.leftという文字列，leftTreeという文字列から得られる情報はほとんど同じなので．
root.left = buildTree(
preorder.sublist(1, leftNodesCount + 1),
inorder.sublist(0, rootIndex),
);
root.right = buildTree(
preorder.sublist(leftNodesCount + 1),
inorder.sublist(rootIndex + 1),
);
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| for (var i = 0; i < inorder.length; i++) { | ||
| if (inorder[i] == rootValue) { | ||
| rootIndex = i; | ||
| break; | ||
| } | ||
| } |
| class Solution { | ||
| TreeNode? buildTree(List<int> preorder, List<int> inorder) { | ||
| int pickInorderRootIndex(List<int> inorder, int rootValue) { | ||
| var rootIndex = 0; |
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全体的に読みやすいです． |
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解いた問題：https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/description/
次に解く問題：https://leetcode.com/problems/paint-fence/description/