diff --git a/notes/Leetcode 题解 - 树.md b/notes/Leetcode 题解 - 树.md index f4c44143..138a3937 100644 --- a/notes/Leetcode 题解 - 树.md +++ b/notes/Leetcode 题解 - 树.md @@ -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 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 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 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 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 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 nums) { ## Trie -

+

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 { } } ``` - diff --git a/notes/pics/lc-tree-trie.png b/notes/pics/lc-tree-trie.png new file mode 100644 index 00000000..881ffd52 Binary files /dev/null and b/notes/pics/lc-tree-trie.png differ