vault backup: 2022-07-05 09:08:49

CS notes/pages/Leetcode Binary-Tree-Inorder-Traversal.md

@@ -18,6 +18,7 @@
 tag:#DFS
 ```
  
+- [[Leetcode Binary-Tree-Postorder-Traversal]]
 - [[Leetcode Binary-Tree-Preorder-Traversal]]
  
 

CS notes/pages/Leetcode Binary-Tree-Postorder-Traversal.md

@@ -0,0 +1,93 @@
+# Leetcode Binary-Tree-Postorder-Traversal
+
+#### 2022-07-04 21:31
+
+> ##### Algorithms:
+> #algorithm  #DFS #DFS_postorder
+> ##### Data structures:
+> #DS #binary_tree 
+> ##### Difficulty:
+> #coding_problem #difficulty-
+> ##### Additional tags:
+> #leetcode  #CS_list_need_practicing 
+> ##### Revisions:
+> N/A
+
+##### Related topics:
+```expander
+tag:#DFS
+```
+ 
+- [[Leetcode Binary-Tree-Inorder-Traversal]]
+- [[Leetcode Binary-Tree-Preorder-Traversal]]
+ 
+
+##### Links:
+- [Link to problem](https://leetcode.com/problems/binary-tree-postorder-traversal/)
+___
+### Problem
+https://leetcode.com/problems/binary-tree-postorder-traversal/
+#### Examples
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2020/08/28/pre1.jpg)
+
+**Input:** root = [1,null,2,3]
+**Output:** [3,2,1]
+
+**Example 2:**
+
+**Input:** root = []
+**Output:** []
+
+**Example 3:**
+
+**Input:** root = [1]
+**Output:** [1]
+
+#### Constraints
+
+-   The number of the nodes in the tree is in the range `[0, 100]`.
+-   `-100 <= Node.val <= 100`
+
+### Thoughts
+
+Same as [[Leetcode Binary-Tree-Inorder-Traversal]] and [[Leetcode Binary-Tree-Preorder-Traversal]]
+
+== TODO: write iteration and another algo #TODO ==
+### Solution
+
+Recursion
+```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 {
+  void postorder(TreeNode *root, vector<int> &answer) {
+    if (root == nullptr) {
+      return;
+    }
+
+    postorder(root->left, answer);
+    postorder(root->right, answer);
+    answer.push_back(root->val);
+  }
+
+public:
+  vector<int> postorderTraversal(TreeNode *root) {
+    vector<int> answer;
+    postorder(root, answer);
+    return answer;
+  }
+};
+
+```

CS notes/pages/Leetcode Binary-Tree-Preorder-Traversal.md

@@ -19,6 +19,7 @@ tag:#DFS
 ```
  
 - [[Leetcode Binary-Tree-Inorder-Traversal]]
+- [[Leetcode Binary-Tree-Postorder-Traversal]]
  
 
 ##### Links: