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@ -172,7 +172,7 @@ comments: true
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```csharp title="build_tree.cs"
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```csharp title="build_tree.cs"
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/* 构建二叉树:分治 */
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/* 构建二叉树:分治 */
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TreeNode Dfs(int[] preorder, Dictionary<int, int> inorderMap, int i, int l, int r) {
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TreeNode DFS(int[] preorder, Dictionary<int, int> inorderMap, int i, int l, int r) {
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// 子树区间为空时终止
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// 子树区间为空时终止
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if (r - l < 0)
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if (r - l < 0)
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return null;
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return null;
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@ -181,9 +181,9 @@ comments: true
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// 查询 m ,从而划分左右子树
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// 查询 m ,从而划分左右子树
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int m = inorderMap[preorder[i]];
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int m = inorderMap[preorder[i]];
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// 子问题:构建左子树
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// 子问题:构建左子树
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root.left = Dfs(preorder, inorderMap, i + 1, l, m - 1);
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root.left = DFS(preorder, inorderMap, i + 1, l, m - 1);
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// 子问题:构建右子树
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// 子问题:构建右子树
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root.right = Dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
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root.right = DFS(preorder, inorderMap, i + 1 + m - l, m + 1, r);
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// 返回根节点
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// 返回根节点
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return root;
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return root;
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}
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}
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@ -195,7 +195,7 @@ comments: true
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for (int i = 0; i < inorder.Length; i++) {
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for (int i = 0; i < inorder.Length; i++) {
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inorderMap.TryAdd(inorder[i], i);
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inorderMap.TryAdd(inorder[i], i);
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}
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}
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TreeNode root = Dfs(preorder, inorderMap, 0, 0, inorder.Length - 1);
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TreeNode root = DFS(preorder, inorderMap, 0, 0, inorder.Length - 1);
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return root;
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return root;
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}
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}
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```
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```
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