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krahets
2023-10-08 01:43:28 +08:00
parent 3d2d669b43
commit baac2d11a7
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zh/chapter_divide_and_conquer/build_binary_tree_problem.md
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@@ -172,30 +172,30 @@ comments: true
```csharp title="build_tree.cs"
/* 构建二叉树：分治 */
TreeNode dfs(int[] preorder, Dictionary<int, int> inorderMap, int i, int l, int r) {
TreeNode Dfs(int[] preorder, Dictionary<int, int> inorderMap, int i, int l, int r) {
// 子树区间为空时终止
if (r - l < 0)
return null;
// 初始化根节点
TreeNode root = new TreeNode(preorder[i]);
TreeNode root = new(preorder[i]);
// 查询 m ，从而划分左右子树
int m = inorderMap[preorder[i]];
// 子问题：构建左子树
root.left = dfs(preorder, inorderMap, i + 1, l, m - 1);
root.left = Dfs(preorder, inorderMap, i + 1, l, m - 1);
// 子问题：构建右子树
root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
root.right = Dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
// 返回根节点
return root;
}
/* 构建二叉树 */
TreeNode buildTree(int[] preorder, int[] inorder) {
TreeNode BuildTree(int[] preorder, int[] inorder) {
// 初始化哈希表，存储 inorder 元素到索引的映射
Dictionary<int, int> inorderMap = new Dictionary<int, int>();
Dictionary<int, int> inorderMap = new();
for (int i = 0; i < inorder.Length; i++) {
inorderMap.TryAdd(inorder[i], i);
}
TreeNode root = dfs(preorder, inorderMap, 0, 0, inorder.Length - 1);
TreeNode root = Dfs(preorder, inorderMap, 0, 0, inorder.Length - 1);
return root;
}
```