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Update Leetcode 题解 - 树.md

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代码经力扣判题验证；前序、中序、后序遍历的递归模板补充递归出口；重新绘制前缀树的配图，难度标注按力扣更新，示例代码块的语言标注改为 text。
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CyC2018
2026-10-28 22:51:09 +08:00
parent aad48aead7
commit 54c70f3784
2 changed files with 36 additions and 34 deletions
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notes/Leetcode 题解 - 树.md
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@@ -63,7 +63,7 @@ public int maxDepth(TreeNode root) {
[Leetcode](https://leetcode.com/problems/balanced-binary-tree/description/) / [力扣](https://leetcode-cn.com/problems/balanced-binary-tree/description/)
```html
```text
3
/ \
9 20
@@ -96,7 +96,7 @@ public int maxDepth(TreeNode root) {
[Leetcode](https://leetcode.com/problems/diameter-of-binary-tree/description/) / [力扣](https://leetcode-cn.com/problems/diameter-of-binary-tree/description/)
```html
```text
Input:
1
@@ -147,7 +147,7 @@ public TreeNode invertTree(TreeNode root) {
[Leetcode](https://leetcode.com/problems/merge-two-binary-trees/description/) / [力扣](https://leetcode-cn.com/problems/merge-two-binary-trees/description/)
```html
```text
Input:
Tree 1 Tree 2
1 2
@@ -182,7 +182,7 @@ Leetcode : 112. Path Sum (Easy)
[Leetcode](https://leetcode.com/problems/path-sum/description/) / [力扣](https://leetcode-cn.com/problems/path-sum/description/)
```html
```text
Given the below binary tree and sum = 22,
5
@@ -208,11 +208,11 @@ public boolean hasPathSum(TreeNode root, int sum) {
### 7. 统计路径和等于一个数的路径数量
437\. Path Sum III (Easy)
437\. Path Sum III (Medium)
[Leetcode](https://leetcode.com/problems/path-sum-iii/description/) / [力扣](https://leetcode-cn.com/problems/path-sum-iii/description/)
```html
```text
root = [10,5,-3,3,2,null,11,3,-2,null,1], sum = 8
10
@@ -254,7 +254,7 @@ private int pathSumStartWithRoot(TreeNode root, long sum) {
[Leetcode](https://leetcode.com/problems/subtree-of-another-tree/description/) / [力扣](https://leetcode-cn.com/problems/subtree-of-another-tree/description/)
```html
```text
Given tree s:
3
/ \
@@ -307,7 +307,7 @@ private boolean isSubtreeWithRoot(TreeNode s, TreeNode t) {
[Leetcode](https://leetcode.com/problems/symmetric-tree/description/) / [力扣](https://leetcode-cn.com/problems/symmetric-tree/description/)
```html
```text
1
/ \
2 2
@@ -353,7 +353,7 @@ public int minDepth(TreeNode root) {
[Leetcode](https://leetcode.com/problems/sum-of-left-leaves/description/) / [力扣](https://leetcode-cn.com/problems/sum-of-left-leaves/description/)
```html
```text
3
/ \
9 20
@@ -378,11 +378,11 @@ private boolean isLeaf(TreeNode node){
### 12. 相同节点值的最大路径长度
687\. Longest Univalue Path (Easy)
687\. Longest Univalue Path (Medium)
[Leetcode](https://leetcode.com/problems/longest-univalue-path/) / [力扣](https://leetcode-cn.com/problems/longest-univalue-path/)
```html
```text
1
/ \
4 5
@@ -417,7 +417,7 @@ private int dfs(TreeNode root){
[Leetcode](https://leetcode.com/problems/house-robber-iii/description/) / [力扣](https://leetcode-cn.com/problems/house-robber-iii/description/)
```html
```text
3
/ \
2 3
@@ -448,7 +448,7 @@ public int rob(TreeNode root) {
[Leetcode](https://leetcode.com/problems/second-minimum-node-in-a-binary-tree/description/) / [力扣](https://leetcode-cn.com/problems/second-minimum-node-in-a-binary-tree/description/)
```html
```text
Input:
2
/ \
@@ -508,11 +508,11 @@ public List<Double> averageOfLevels(TreeNode root) {
### 2. 得到左下角的节点
513\. Find Bottom Left Tree Value (Easy)
513\. Find Bottom Left Tree Value (Medium)
[Leetcode](https://leetcode.com/problems/find-bottom-left-tree-value/description/) / [力扣](https://leetcode-cn.com/problems/find-bottom-left-tree-value/description/)
```html
```text
Input:
1
@@ -542,7 +542,7 @@ public int findBottomLeftValue(TreeNode root) {
## 前中后序遍历
```html
```text
1
/ \
2 3
@@ -557,12 +557,13 @@ public int findBottomLeftValue(TreeNode root) {
层次遍历使用 BFS 实现，利用的就是 BFS 一层一层遍历的特性；而前序、中序、后序遍历利用了 DFS 实现。
前序、中序、后序遍只是在对节点访问的顺序有一点不同，其它都相同。
前序、中序、后序遍历只是在对节点访问的顺序有一点不同，其它都相同。
① 前序
```java
void dfs(TreeNode root) {
if (root == null) return;
visit(root);
dfs(root.left);
dfs(root.right);
@@ -573,6 +574,7 @@ void dfs(TreeNode root) {
```java
void dfs(TreeNode root) {
if (root == null) return;
dfs(root.left);
visit(root);
dfs(root.right);
@@ -583,6 +585,7 @@ void dfs(TreeNode root) {
```java
void dfs(TreeNode root) {
if (root == null) return;
dfs(root.left);
dfs(root.right);
visit(root);
@@ -591,7 +594,7 @@ void dfs(TreeNode root) {
### 1. 非递归实现二叉树的前序遍历
144\. Binary Tree Preorder Traversal (Medium)
144\. Binary Tree Preorder Traversal (Easy)
[Leetcode](https://leetcode.com/problems/binary-tree-preorder-traversal/description/) / [力扣](https://leetcode-cn.com/problems/binary-tree-preorder-traversal/description/)
@@ -613,7 +616,7 @@ public List<Integer> preorderTraversal(TreeNode root) {
### 2. 非递归实现二叉树的后序遍历
145\. Binary Tree Postorder Traversal (Medium)
145\. Binary Tree Postorder Traversal (Easy)
[Leetcode](https://leetcode.com/problems/binary-tree-postorder-traversal/description/) / [力扣](https://leetcode-cn.com/problems/binary-tree-postorder-traversal/description/)
@@ -638,7 +641,7 @@ public List<Integer> postorderTraversal(TreeNode root) {
### 3. 非递归实现二叉树的中序遍历
94\. Binary Tree Inorder Traversal (Medium)
94\. Binary Tree Inorder Traversal (Easy)
[Leetcode](https://leetcode.com/problems/binary-tree-inorder-traversal/description/) / [力扣](https://leetcode-cn.com/problems/binary-tree-inorder-traversal/description/)
@@ -669,11 +672,11 @@ public List<Integer> inorderTraversal(TreeNode root) {
### 1. 修剪二叉查找树
669\. Trim a Binary Search Tree (Easy)
669\. Trim a Binary Search Tree (Medium)
[Leetcode](https://leetcode.com/problems/trim-a-binary-search-tree/description/) / [力扣](https://leetcode-cn.com/problems/trim-a-binary-search-tree/description/)
```html
```text
Input:
3
@@ -757,11 +760,11 @@ private int count(TreeNode node) {
### 3. 把二叉查找树每个节点的值都加上比它大的节点的值
538\. Convert BST to Greater Tree (Easy)
538\. Convert BST to Greater Tree (Medium)
[Leetcode](https://leetcode.com/problems/convert-bst-to-greater-tree/description/) / [力扣](https://leetcode-cn.com/problems/convert-bst-to-greater-tree/description/)
```html
```text
Input: The root of a Binary Search Tree like this:
5
@@ -796,11 +799,11 @@ private void traver(TreeNode node) {
### 4. 二叉查找树的最近公共祖先
235\. Lowest Common Ancestor of a Binary Search Tree (Easy)
235\. Lowest Common Ancestor of a Binary Search Tree (Medium)
[Leetcode](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/description/) / [力扣](https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-search-tree/description/)
```html
```text
_______6______
/ \
___2__ ___8__
@@ -826,7 +829,7 @@ public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
[Leetcode](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/description/) / [力扣](https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-tree/description/)
```html
```text
_______3______
/ \
___5__ ___1__
@@ -874,7 +877,7 @@ private TreeNode toBST(int[] nums, int sIdx, int eIdx){
[Leetcode](https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/description/) / [力扣](https://leetcode-cn.com/problems/convert-sorted-list-to-binary-search-tree/description/)
```html
```text
Given the sorted linked list: [-10,-3,0,5,9],
One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST:
@@ -917,7 +920,7 @@ private ListNode preMid(ListNode head) {
[Leetcode](https://leetcode.com/problems/two-sum-iv-input-is-a-bst/description/) / [力扣](https://leetcode-cn.com/problems/two-sum-iv-input-is-a-bst/description/)
```html
```text
Input:
5
@@ -963,7 +966,7 @@ private void inOrder(TreeNode root, List<Integer> nums) {
[Leetcode](https://leetcode.com/problems/minimum-absolute-difference-in-bst/description/) / [力扣](https://leetcode-cn.com/problems/minimum-absolute-difference-in-bst/description/)
```html
```text
Input:
1
@@ -1003,7 +1006,7 @@ private void inOrder(TreeNode node) {
[Leetcode](https://leetcode.com/problems/find-mode-in-binary-search-tree/description/) / [力扣](https://leetcode-cn.com/problems/find-mode-in-binary-search-tree/description/)
```html
```text
1
\
2
@@ -1052,7 +1055,7 @@ private void inOrder(TreeNode node, List<Integer> nums) {
## Trie
<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/5c638d59-d4ae-4ba4-ad44-80bdc30f38dd.jpg"/> </div><br>
<div align="center"> <img src="pics/lc-tree-trie.png" width="580px"/> </div><br>
Trie，又称前缀树或字典树，用于判断字符串是否存在或者是否具有某种字符串前缀。
@@ -1126,7 +1129,7 @@ class Trie {
[Leetcode](https://leetcode.com/problems/map-sum-pairs/description/) / [力扣](https://leetcode-cn.com/problems/map-sum-pairs/description/)
```html
```text
Input: insert("apple", 3), Output: Null
Input: sum("ap"), Output: 3
Input: insert("app", 2), Output: Null
@@ -1186,4 +1189,3 @@ class MapSum {
}
}
```
notes/pics/lc-tree-trie.png
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