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@ -77,8 +77,7 @@ status: new
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```python title="build_tree.py"
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```python title="build_tree.py"
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def dfs(
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def dfs(
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preorder: list[int],
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preorder: list[int],
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inorder: list[int],
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inorder_map: dict[int, int],
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hmap: dict[int, int],
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i: int,
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i: int,
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l: int,
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l: int,
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r: int,
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r: int,
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@ -90,19 +89,19 @@ status: new
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# 初始化根节点
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# 初始化根节点
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root = TreeNode(preorder[i])
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root = TreeNode(preorder[i])
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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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m = hmap[preorder[i]]
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m = inorder_map[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, inorder, hmap, i + 1, l, m - 1)
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root.left = dfs(preorder, inorder_map, 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, inorder, hmap, i + 1 + m - l, m + 1, r)
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root.right = dfs(preorder, inorder_map, 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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def build_tree(preorder: list[int], inorder: list[int]) -> TreeNode | None:
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def build_tree(preorder: list[int], inorder: list[int]) -> TreeNode | None:
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"""构建二叉树"""
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"""构建二叉树"""
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# 初始化哈希表,存储 inorder 元素到索引的映射
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# 初始化哈希表,存储 inorder 元素到索引的映射
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hmap = {val: i for i, val in enumerate(inorder)}
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inorder_map = {val: i for i, val in enumerate(inorder)}
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root = dfs(preorder, inorder, hmap, 0, 0, len(inorder) - 1)
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root = dfs(preorder, inorder_map, 0, 0, len(inorder) - 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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@ -110,18 +109,18 @@ status: new
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```cpp title="build_tree.cpp"
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```cpp title="build_tree.cpp"
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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(vector<int> &preorder, vector<int> &inorder, unordered_map<int, int> &hmap, int i, int l, int r) {
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TreeNode *dfs(vector<int> &preorder, unordered_map<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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// 初始化根节点
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// 初始化根节点
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TreeNode *root = new TreeNode(preorder[i]);
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TreeNode *root = new TreeNode(preorder[i]);
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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 = hmap[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, inorder, hmap, 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, inorder, hmap, 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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@ -129,11 +128,11 @@ status: new
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/* 构建二叉树 */
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/* 构建二叉树 */
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TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
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TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
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// 初始化哈希表,存储 inorder 元素到索引的映射
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// 初始化哈希表,存储 inorder 元素到索引的映射
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unordered_map<int, int> hmap;
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unordered_map<int, int> inorderMap;
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for (int i = 0; i < inorder.size(); i++) {
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for (int i = 0; i < inorder.size(); i++) {
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hmap[inorder[i]] = i;
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inorderMap[inorder[i]] = i;
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}
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}
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TreeNode *root = dfs(preorder, inorder, hmap, 0, 0, inorder.size() - 1);
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TreeNode *root = dfs(preorder, inorderMap, 0, 0, inorder.size() - 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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@ -142,18 +141,18 @@ status: new
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```java title="build_tree.java"
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```java title="build_tree.java"
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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, int[] inorder, Map<Integer, Integer> hmap, int i, int l, int r) {
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TreeNode dfs(int[] preorder, Map<Integer, Integer> 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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// 初始化根节点
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// 初始化根节点
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TreeNode root = new TreeNode(preorder[i]);
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TreeNode root = new TreeNode(preorder[i]);
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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 = hmap.get(preorder[i]);
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int m = inorderMap.get(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, inorder, hmap, 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, inorder, hmap, 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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@ -161,11 +160,11 @@ status: new
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/* 构建二叉树 */
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/* 构建二叉树 */
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TreeNode buildTree(int[] preorder, int[] inorder) {
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TreeNode buildTree(int[] preorder, int[] inorder) {
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// 初始化哈希表,存储 inorder 元素到索引的映射
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// 初始化哈希表,存储 inorder 元素到索引的映射
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Map<Integer, Integer> hmap = new HashMap<>();
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Map<Integer, Integer> inorderMap = new HashMap<>();
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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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hmap.put(inorder[i], i);
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inorderMap.put(inorder[i], i);
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}
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}
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TreeNode root = dfs(preorder, inorder, hmap, 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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@ -174,18 +173,18 @@ status: new
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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, int[] inorder, Dictionary<int, int> hmap, 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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// 初始化根节点
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// 初始化根节点
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TreeNode root = new TreeNode(preorder[i]);
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TreeNode root = new TreeNode(preorder[i]);
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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 = hmap[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, inorder, hmap, 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, inorder, hmap, 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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@ -193,11 +192,11 @@ status: new
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/* 构建二叉树 */
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/* 构建二叉树 */
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TreeNode buildTree(int[] preorder, int[] inorder) {
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TreeNode buildTree(int[] preorder, int[] inorder) {
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// 初始化哈希表,存储 inorder 元素到索引的映射
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// 初始化哈希表,存储 inorder 元素到索引的映射
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Dictionary<int, int> hmap = new Dictionary<int, int>();
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Dictionary<int, int> inorderMap = new Dictionary<int, int>();
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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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hmap.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, inorder, hmap, 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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@ -206,7 +205,7 @@ status: new
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```go title="build_tree.go"
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```go title="build_tree.go"
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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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func dfsBuildTree(preorder, inorder []int, hmap map[int]int, i, l, r int) *TreeNode {
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func dfsBuildTree(preorder []int, inorderMap map[int]int, i, l, r int) *TreeNode {
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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 nil
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return nil
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@ -214,11 +213,11 @@ status: new
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// 初始化根节点
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// 初始化根节点
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root := NewTreeNode(preorder[i])
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root := NewTreeNode(preorder[i])
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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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m := hmap[preorder[i]]
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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 = dfsBuildTree(preorder, inorder, hmap, i+1, l, m-1)
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root.Left = dfsBuildTree(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 = dfsBuildTree(preorder, inorder, hmap, i+1+m-l, m+1, r)
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root.Right = dfsBuildTree(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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|
@ -226,12 +225,12 @@ status: new
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|
/* 构建二叉树 */
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|
/* 构建二叉树 */
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|
func buildTree(preorder, inorder []int) *TreeNode {
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|
|
func buildTree(preorder, inorder []int) *TreeNode {
|
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|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
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|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
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|
|
hmap := make(map[int]int, len(inorder))
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|
|
inorderMap := make(map[int]int, len(inorder))
|
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|
|
for i := 0; i < len(inorder); i++ {
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|
for i := 0; i < len(inorder); i++ {
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|
hmap[inorder[i]] = i
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|
inorderMap[inorder[i]] = i
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}
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}
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|
root := dfsBuildTree(preorder, inorder, hmap, 0, 0, len(inorder)-1)
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|
|
root := dfsBuildTree(preorder, inorderMap, 0, 0, len(inorder)-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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|
|
@ -240,7 +239,7 @@ status: new
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|
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|
|
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|
|
```swift title="build_tree.swift"
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|
|
|
```swift title="build_tree.swift"
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|
|
|
/* 构建二叉树:分治 */
|
|
|
|
/* 构建二叉树:分治 */
|
|
|
|
func dfs(preorder: [Int], inorder: [Int], hmap: [Int: Int], i: Int, l: Int, r: Int) -> TreeNode? {
|
|
|
|
func dfs(preorder: [Int], inorderMap: [Int: Int], i: Int, l: Int, r: Int) -> TreeNode? {
|
|
|
|
// 子树区间为空时终止
|
|
|
|
// 子树区间为空时终止
|
|
|
|
if r - l < 0 {
|
|
|
|
if r - l < 0 {
|
|
|
|
return nil
|
|
|
|
return nil
|
|
|
@ -248,11 +247,11 @@ status: new
|
|
|
|
// 初始化根节点
|
|
|
|
// 初始化根节点
|
|
|
|
let root = TreeNode(x: preorder[i])
|
|
|
|
let root = TreeNode(x: preorder[i])
|
|
|
|
// 查询 m ,从而划分左右子树
|
|
|
|
// 查询 m ,从而划分左右子树
|
|
|
|
let m = hmap[preorder[i]]!
|
|
|
|
let m = inorderMap[preorder[i]]!
|
|
|
|
// 子问题:构建左子树
|
|
|
|
// 子问题:构建左子树
|
|
|
|
root.left = dfs(preorder: preorder, inorder: inorder, hmap: hmap, i: i + 1, l: l, r: m - 1)
|
|
|
|
root.left = dfs(preorder: preorder, inorderMap: inorderMap, i: i + 1, l: l, r: m - 1)
|
|
|
|
// 子问题:构建右子树
|
|
|
|
// 子问题:构建右子树
|
|
|
|
root.right = dfs(preorder: preorder, inorder: inorder, hmap: hmap, i: i + 1 + m - l, l: m + 1, r: r)
|
|
|
|
root.right = dfs(preorder: preorder, inorderMap: inorderMap, i: i + 1 + m - l, l: m + 1, r: r)
|
|
|
|
// 返回根节点
|
|
|
|
// 返回根节点
|
|
|
|
return root
|
|
|
|
return root
|
|
|
|
}
|
|
|
|
}
|
|
|
@ -260,8 +259,8 @@ status: new
|
|
|
|
/* 构建二叉树 */
|
|
|
|
/* 构建二叉树 */
|
|
|
|
func buildTree(preorder: [Int], inorder: [Int]) -> TreeNode? {
|
|
|
|
func buildTree(preorder: [Int], inorder: [Int]) -> TreeNode? {
|
|
|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
|
|
let hmap = inorder.enumerated().reduce(into: [:]) { $0[$1.element] = $1.offset }
|
|
|
|
let inorderMap = inorder.enumerated().reduce(into: [:]) { $0[$1.element] = $1.offset }
|
|
|
|
return dfs(preorder: preorder, inorder: inorder, hmap: hmap, i: 0, l: 0, r: inorder.count - 1)
|
|
|
|
return dfs(preorder: preorder, inorderMap: inorderMap, i: 0, l: 0, r: inorder.count - 1)
|
|
|
|
}
|
|
|
|
}
|
|
|
|
```
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
|
@ -269,17 +268,17 @@ status: new
|
|
|
|
|
|
|
|
|
|
|
|
```javascript title="build_tree.js"
|
|
|
|
```javascript title="build_tree.js"
|
|
|
|
/* 构建二叉树:分治 */
|
|
|
|
/* 构建二叉树:分治 */
|
|
|
|
function dfs(preorder, inorder, hmap, i, l, r) {
|
|
|
|
function dfs(preorder, inorderMap, i, l, r) {
|
|
|
|
// 子树区间为空时终止
|
|
|
|
// 子树区间为空时终止
|
|
|
|
if (r - l < 0) return null;
|
|
|
|
if (r - l < 0) return null;
|
|
|
|
// 初始化根节点
|
|
|
|
// 初始化根节点
|
|
|
|
const root = new TreeNode(preorder[i]);
|
|
|
|
const root = new TreeNode(preorder[i]);
|
|
|
|
// 查询 m ,从而划分左右子树
|
|
|
|
// 查询 m ,从而划分左右子树
|
|
|
|
const m = hmap.get(preorder[i]);
|
|
|
|
const m = inorderMap.get(preorder[i]);
|
|
|
|
// 子问题:构建左子树
|
|
|
|
// 子问题:构建左子树
|
|
|
|
root.left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
|
|
|
|
root.left = dfs(preorder, inorderMap, i + 1, l, m - 1);
|
|
|
|
// 子问题:构建右子树
|
|
|
|
// 子问题:构建右子树
|
|
|
|
root.right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
|
|
|
|
root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
|
|
|
|
// 返回根节点
|
|
|
|
// 返回根节点
|
|
|
|
return root;
|
|
|
|
return root;
|
|
|
|
}
|
|
|
|
}
|
|
|
@ -287,11 +286,11 @@ status: new
|
|
|
|
/* 构建二叉树 */
|
|
|
|
/* 构建二叉树 */
|
|
|
|
function buildTree(preorder, inorder) {
|
|
|
|
function buildTree(preorder, inorder) {
|
|
|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
|
|
let hmap = new Map();
|
|
|
|
let inorderMap = new Map();
|
|
|
|
for (let i = 0; i < inorder.length; i++) {
|
|
|
|
for (let i = 0; i < inorder.length; i++) {
|
|
|
|
hmap.set(inorder[i], i);
|
|
|
|
inorderMap.set(inorder[i], i);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
const root = dfs(preorder, inorder, hmap, 0, 0, inorder.length - 1);
|
|
|
|
const root = dfs(preorder, inorderMap, 0, 0, inorder.length - 1);
|
|
|
|
return root;
|
|
|
|
return root;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
```
|
|
|
|
```
|
|
|
@ -302,8 +301,7 @@ status: new
|
|
|
|
/* 构建二叉树:分治 */
|
|
|
|
/* 构建二叉树:分治 */
|
|
|
|
function dfs(
|
|
|
|
function dfs(
|
|
|
|
preorder: number[],
|
|
|
|
preorder: number[],
|
|
|
|
inorder: number[],
|
|
|
|
inorderMap: Map<number, number>,
|
|
|
|
hmap: Map<number, number>,
|
|
|
|
|
|
|
|
i: number,
|
|
|
|
i: number,
|
|
|
|
l: number,
|
|
|
|
l: number,
|
|
|
|
r: number
|
|
|
|
r: number
|
|
|
@ -313,11 +311,11 @@ status: new
|
|
|
|
// 初始化根节点
|
|
|
|
// 初始化根节点
|
|
|
|
const root: TreeNode = new TreeNode(preorder[i]);
|
|
|
|
const root: TreeNode = new TreeNode(preorder[i]);
|
|
|
|
// 查询 m ,从而划分左右子树
|
|
|
|
// 查询 m ,从而划分左右子树
|
|
|
|
const m = hmap.get(preorder[i]);
|
|
|
|
const m = inorderMap.get(preorder[i]);
|
|
|
|
// 子问题:构建左子树
|
|
|
|
// 子问题:构建左子树
|
|
|
|
root.left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
|
|
|
|
root.left = dfs(preorder, inorderMap, i + 1, l, m - 1);
|
|
|
|
// 子问题:构建右子树
|
|
|
|
// 子问题:构建右子树
|
|
|
|
root.right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
|
|
|
|
root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
|
|
|
|
// 返回根节点
|
|
|
|
// 返回根节点
|
|
|
|
return root;
|
|
|
|
return root;
|
|
|
|
}
|
|
|
|
}
|
|
|
@ -325,11 +323,11 @@ status: new
|
|
|
|
/* 构建二叉树 */
|
|
|
|
/* 构建二叉树 */
|
|
|
|
function buildTree(preorder: number[], inorder: number[]): TreeNode | null {
|
|
|
|
function buildTree(preorder: number[], inorder: number[]): TreeNode | null {
|
|
|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
|
|
let hmap = new Map<number, number>();
|
|
|
|
let inorderMap = new Map<number, number>();
|
|
|
|
for (let i = 0; i < inorder.length; i++) {
|
|
|
|
for (let i = 0; i < inorder.length; i++) {
|
|
|
|
hmap.set(inorder[i], i);
|
|
|
|
inorderMap.set(inorder[i], i);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
const root = dfs(preorder, inorder, hmap, 0, 0, inorder.length - 1);
|
|
|
|
const root = dfs(preorder, inorderMap, 0, 0, inorder.length - 1);
|
|
|
|
return root;
|
|
|
|
return root;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
```
|
|
|
|
```
|
|
|
@ -340,8 +338,7 @@ status: new
|
|
|
|
/* 构建二叉树:分治 */
|
|
|
|
/* 构建二叉树:分治 */
|
|
|
|
TreeNode? dfs(
|
|
|
|
TreeNode? dfs(
|
|
|
|
List<int> preorder,
|
|
|
|
List<int> preorder,
|
|
|
|
List<int> inorder,
|
|
|
|
Map<int, int> inorderMap,
|
|
|
|
Map<int, int> hmap,
|
|
|
|
|
|
|
|
int i,
|
|
|
|
int i,
|
|
|
|
int l,
|
|
|
|
int l,
|
|
|
|
int r,
|
|
|
|
int r,
|
|
|
@ -353,11 +350,11 @@ status: new
|
|
|
|
// 初始化根节点
|
|
|
|
// 初始化根节点
|
|
|
|
TreeNode? root = TreeNode(preorder[i]);
|
|
|
|
TreeNode? root = TreeNode(preorder[i]);
|
|
|
|
// 查询 m ,从而划分左右子树
|
|
|
|
// 查询 m ,从而划分左右子树
|
|
|
|
int m = hmap[preorder[i]]!;
|
|
|
|
int m = inorderMap[preorder[i]]!;
|
|
|
|
// 子问题:构建左子树
|
|
|
|
// 子问题:构建左子树
|
|
|
|
root.left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
|
|
|
|
root.left = dfs(preorder, inorderMap, i + 1, l, m - 1);
|
|
|
|
// 子问题:构建右子树
|
|
|
|
// 子问题:构建右子树
|
|
|
|
root.right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
|
|
|
|
root.right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
|
|
|
|
// 返回根节点
|
|
|
|
// 返回根节点
|
|
|
|
return root;
|
|
|
|
return root;
|
|
|
|
}
|
|
|
|
}
|
|
|
@ -365,11 +362,11 @@ status: new
|
|
|
|
/* 构建二叉树 */
|
|
|
|
/* 构建二叉树 */
|
|
|
|
TreeNode? buildTree(List<int> preorder, List<int> inorder) {
|
|
|
|
TreeNode? buildTree(List<int> preorder, List<int> inorder) {
|
|
|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
|
|
Map<int, int> hmap = {};
|
|
|
|
Map<int, int> inorderMap = {};
|
|
|
|
for (int i = 0; i < inorder.length; i++) {
|
|
|
|
for (int i = 0; i < inorder.length; i++) {
|
|
|
|
hmap[inorder[i]] = i;
|
|
|
|
inorderMap[inorder[i]] = i;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
TreeNode? root = dfs(preorder, inorder, hmap, 0, 0, inorder.length - 1);
|
|
|
|
TreeNode? root = dfs(preorder, inorderMap, 0, 0, inorder.length - 1);
|
|
|
|
return root;
|
|
|
|
return root;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
```
|
|
|
|
```
|
|
|
@ -378,17 +375,17 @@ status: new
|
|
|
|
|
|
|
|
|
|
|
|
```rust title="build_tree.rs"
|
|
|
|
```rust title="build_tree.rs"
|
|
|
|
/* 构建二叉树:分治 */
|
|
|
|
/* 构建二叉树:分治 */
|
|
|
|
fn dfs(preorder: &[i32], inorder: &[i32], hmap: &HashMap<i32, i32>, i: i32, l: i32, r: i32) -> Option<Rc<RefCell<TreeNode>>> {
|
|
|
|
fn dfs(preorder: &[i32], inorderMap: &HashMap<i32, i32>, i: i32, l: i32, r: i32) -> Option<Rc<RefCell<TreeNode>>> {
|
|
|
|
// 子树区间为空时终止
|
|
|
|
// 子树区间为空时终止
|
|
|
|
if r - l < 0 { return None; }
|
|
|
|
if r - l < 0 { return None; }
|
|
|
|
// 初始化根节点
|
|
|
|
// 初始化根节点
|
|
|
|
let root = TreeNode::new(preorder[i as usize]);
|
|
|
|
let root = TreeNode::new(preorder[i as usize]);
|
|
|
|
// 查询 m ,从而划分左右子树
|
|
|
|
// 查询 m ,从而划分左右子树
|
|
|
|
let m = hmap.get(&preorder[i as usize]).unwrap();
|
|
|
|
let m = inorderMap.get(&preorder[i as usize]).unwrap();
|
|
|
|
// 子问题:构建左子树
|
|
|
|
// 子问题:构建左子树
|
|
|
|
root.borrow_mut().left = dfs(preorder, inorder, hmap, i + 1, l, m - 1);
|
|
|
|
root.borrow_mut().left = dfs(preorder, inorderMap, i + 1, l, m - 1);
|
|
|
|
// 子问题:构建右子树
|
|
|
|
// 子问题:构建右子树
|
|
|
|
root.borrow_mut().right = dfs(preorder, inorder, hmap, i + 1 + m - l, m + 1, r);
|
|
|
|
root.borrow_mut().right = dfs(preorder, inorderMap, i + 1 + m - l, m + 1, r);
|
|
|
|
// 返回根节点
|
|
|
|
// 返回根节点
|
|
|
|
Some(root)
|
|
|
|
Some(root)
|
|
|
|
}
|
|
|
|
}
|
|
|
@ -396,11 +393,11 @@ status: new
|
|
|
|
/* 构建二叉树 */
|
|
|
|
/* 构建二叉树 */
|
|
|
|
fn build_tree(preorder: &[i32], inorder: &[i32]) -> Option<Rc<RefCell<TreeNode>>> {
|
|
|
|
fn build_tree(preorder: &[i32], inorder: &[i32]) -> Option<Rc<RefCell<TreeNode>>> {
|
|
|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
|
|
// 初始化哈希表,存储 inorder 元素到索引的映射
|
|
|
|
let mut hmap: HashMap<i32, i32> = HashMap::new();
|
|
|
|
let mut inorderMap: HashMap<i32, i32> = HashMap::new();
|
|
|
|
for i in 0..inorder.len() {
|
|
|
|
for i in 0..inorder.len() {
|
|
|
|
hmap.insert(inorder[i], i as i32);
|
|
|
|
inorderMap.insert(inorder[i], i as i32);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
let root = dfs(preorder, inorder, &hmap, 0, 0, inorder.len() as i32 - 1);
|
|
|
|
let root = dfs(preorder, &inorderMap, 0, 0, inorder.len() as i32 - 1);
|
|
|
|
root
|
|
|
|
root
|
|
|
|
}
|
|
|
|
}
|
|
|
|
```
|
|
|
|
```
|
|
|
|