vault backup: 2022-07-05 09:44:58

.obsidian/graph.json

@@ -32,6 +32,6 @@
   "repelStrength": 10,
   "linkStrength": 1,
   "linkDistance": 250,
-  "scale": 0.9752800867986091,
+  "scale": 0.975280086798608,
   "close": true
 }

CS notes/CS-index.md

@@ -20,6 +20,8 @@ tag:#CS_list_need_understanding
 - [ ] [[$filename]]
 ```
  
+- [ ] [[Leetcode Binary-Tree-Preorder-Traversal]]
+- [ ] [[Leetcode Implement-Queue-Using-Stacks]]
 - [ ] [[Leetcode Reverse-Linked-List]]
  
 
@@ -30,6 +32,7 @@ tag:#CS_list_need_practicing
 - [ ] [[$filename]]
 ```
  
+- [ ] [[Leetcode Binary-Tree-Postorder-Traversal]]
 - [ ] [[Leetcode Reverse-Linked-List]]
  
 
@@ -45,9 +48,16 @@ tag:#leetcode
  
 - [[Leetcode  Valid-Parentheses]]
 - [[Leetcode Best-Time-To-Buy-And-Sell-Stock]]
+- [[Leetcode Binary-Tree-Inorder-Traversal]]
+- [[Leetcode Binary-Tree-Level-Order-Traversal]]
+- [[Leetcode Binary-Tree-Postorder-Traversal]]
+- [[Leetcode Binary-Tree-Preorder-Traversal]]
 - [[Leetcode First-Unique-Character-In-a-String]]
+- [[Leetcode Implement-Queue-Using-Stacks]]
 - [[Leetcode Intersection-of-Two-Arrays-II]]
 - [[Leetcode Linked-List-Cycle]]
+- [[Leetcode Maximum-Depth-Of-Binary-Tree]]
+- [[Leetcode Maximum-Difference-Between-Increasing-Elements]]
 - [[Leetcode Maxinum-subarray]]
 - [[Leetcode Merge-Sorted-Array]]
 - [[Leetcode Merge-Two-Sorted-Lists]]
@@ -86,9 +96,15 @@ tag:#DS tag:#coding_problem -tag:#template_remove_me
  
 - [[Leetcode  Valid-Parentheses]]
 - [[Leetcode Best-Time-To-Buy-And-Sell-Stock]]
+- [[Leetcode Binary-Tree-Inorder-Traversal]]
+- [[Leetcode Binary-Tree-Level-Order-Traversal]]
+- [[Leetcode Binary-Tree-Postorder-Traversal]]
+- [[Leetcode Binary-Tree-Preorder-Traversal]]
 - [[Leetcode First-Unique-Character-In-a-String]]
+- [[Leetcode Implement-Queue-Using-Stacks]]
 - [[Leetcode Intersection-of-Two-Arrays-II]]
 - [[Leetcode Linked-List-Cycle]]
+- [[Leetcode Maximum-Depth-Of-Binary-Tree]]
 - [[Leetcode Maxinum-subarray]]
 - [[Leetcode Merge-Sorted-Array]]
 - [[Leetcode Merge-Two-Sorted-Lists]]
@@ -126,9 +142,15 @@ tag:#algorithm tag:#coding_problem -tag:#template_remove_me
 ```
  
 - [[Leetcode Best-Time-To-Buy-And-Sell-Stock]]
+- [[Leetcode Binary-Tree-Inorder-Traversal]]
+- [[Leetcode Binary-Tree-Level-Order-Traversal]]
+- [[Leetcode Binary-Tree-Postorder-Traversal]]
+- [[Leetcode Binary-Tree-Preorder-Traversal]]
 - [[Leetcode First-Unique-Character-In-a-String]]
 - [[Leetcode Intersection-of-Two-Arrays-II]]
 - [[Leetcode Linked-List-Cycle]]
+- [[Leetcode Maximum-Depth-Of-Binary-Tree]]
+- [[Leetcode Maximum-Difference-Between-Increasing-Elements]]
 - [[Leetcode Maxinum-subarray]]
 - [[Leetcode Merge-Sorted-Array]]
 - [[Leetcode Merge-Two-Sorted-Lists]]

CS notes/pages/Leetcode Binary-Tree-Level-Order-Traversal.md

@@ -31,13 +31,13 @@ Given the `root` of a binary tree, return _the level order traversal of its node
 
 ![](https://assets.leetcode.com/uploads/2021/02/19/tree1.jpg)
 
-**Input:** root = [3,9,20,null,null,15,7]
+**Input:** root = `[3,9,20,null,null,15,7]`
-**Output:** [[3],[9,20],[15,7]]
+**Output:** `[[3],[9,20],[15,7]]`
 
 **Example 2:**
 
 **Input:** root = [1]
-**Output:** [[1]]
+**Output:** `[[1]]`
 
 **Example 3:**
 
@@ -58,7 +58,7 @@ In contrary to DFS, BFS uses queue. and there are many tricks for pushing 2d arr
 vector<vector<int>> vec;
 vec.push_back({});
 vec.back().push_back(5);
-// [[5]]
+// [[ 5 ]]
 ```
 ### Solution
 

CS notes/pages/Leetcode Implement-Queue-Using-Stacks.md

@@ -38,8 +38,10 @@ Implement the `MyQueue` class:
 
 #### Examples
 **Input**
+```
 ["MyQueue", "push", "push", "peek", "pop", "empty"]
 [[], [1], [2], [], [], []]
+```
 **Output**
 [null, null, null, 1, 1, false]
 

CS notes/pages/Leetcode Maximum-Depth-Of-Binary-Tree.md

@@ -21,17 +21,87 @@ tag:#BFS
  
 
 ##### Links:
-- [Link to problem]()
+- [Link to problem](https://leetcode.com/problems/maximum-depth-of-binary-tree/)
 ___
 ### Problem
+Given the `root` of a binary tree, return _its maximum depth_.
+
+A binary tree's **maximum depth** is the number of nodes along the longest path from the root node down to the farthest leaf node.
 
 #### Examples
 
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2020/11/26/tmp-tree.jpg)
+
+**Input:** root = [3,9,20,null,null,15,7]
+**Output:** 3
+
+**Example 2:**
+
+**Input:** root = [1,null,2]
+**Output:** 2
+
 #### Constraints
 
+-   The number of nodes in the tree is in the range `[0, 104]`.
+-   `-100 <= Node.val <= 100`
+
 ### Thoughts
 
 > [!summary]
-> This is a #template_remove_me
+> This problem can be solved by #BFS or #DFS
+
+BFS way:
+Simply log the level in each while iteration.
+
+DFS way: (Popular)
+Use recursion
 
 ### Solution
+
+DFS Recursion:
+```cpp
+```
+
+BFS:
+```cpp
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left),
+ * right(right) {}
+ * };
+ */
+class Solution {
+public:
+  int maxDepth(TreeNode *root) {
+    // BFS
+    int levels = 0;
+    queue<TreeNode *> pending;
+    TreeNode *ptr = root;
+    if (ptr)
+      pending.push(ptr);
+
+    while (!pending.empty()) {
+      levels++;
+      for (int i = 0, size = pending.size(); i < size; i++) {
+        ptr = pending.front();
+        pending.pop();
+
+        if (ptr->left)
+          pending.push(ptr->left);
+        if (ptr->right)
+          pending.push(ptr->right);
+      }
+    }
+
+    return levels;
+  }
+};
+```