update

Author: yennanliu

README.md

@@ -782,7 +782,7 @@
 337| [House Robber III](https://leetcode.com/problems/house-robber-iii/) | [Python](./leetcode_python/Recursion/house-robber-iii.py)  | _O(n)_ _O(h)_| Medium|amazon, google| AGAIN (not start)
 395| [Longest Substring with At Least K Repeating Characters](https://leetcode.com/problems/longest-substring-with-at-least-k-repeating-characters/) |[Python](./leetcode_python/Recursion/longest-substring-with-at-least-k-repeating-characters.py)  | _O(n)_  | _O(1)_  | Medium |`AGAIN`,`recursion`, `good trick`,`fb`| AGAIN************ (4)
 404| [Sum of Left Leaves](https://leetcode.com/problems/sum-of-left-leaves/) | [Python](./leetcode_python/Recursion/sum-of-left-leaves.py)  | _O(n)_ | _O(h)_ | Easy, tree, bfs, dfs |`fb`| OK**** (3) 
-437| [Path Sum III](https://leetcode.com/problems/path-sum-iii/) | [Python](./leetcode_python/Recursion/path-sum-iii.py) | _O(n)_ | _O(h)_ |Easy|`good trick`,`UBER`, `AMAZON`, `fb`| AGAIN*** (3)
+437| [Path Sum III](https://leetcode.com/problems/path-sum-iii/) | [Python](./leetcode_python/Recursion/path-sum-iii.py) | _O(n)_ | _O(h)_ |Medium|`good trick`,`UBER`, `AMAZON`, `fb`| AGAIN*** (3)
 544| [Output Contest Matches](https://leetcode.com/problems/output-contest-matches/) | [Python](./leetcode_python/Recursion/output-contest-matches.py)  | _O(n)_          | _O(n)_          | Medium           || AGAIN 
 549 | [Binary Tree Longest Consecutive Sequence II](https://leetcode.com/problems/binary-tree-longest-consecutive-sequence-ii/) | [Python](./leetcode_python/Recursion/binary-tree-longest-consecutive-sequence-ii.py)  | _O(n)_ | _O(h)_ | Medium    |🔒| AGAIN (not start)
 669| [Trim a Binary Search Tree](https://leetcode.com/problems/trim-a-binary-search-tree/) | [Python](./leetcode_python/Recursion/trim-a-binary-search-tree.py) | _O(n)_ | _O(h)_ | Medium |good basic, BST, dfs, recursion,`amazon`| AGAIN******* (4)

leetcode_python/Recursion/path-sum-iii.py

@@ -1,3 +1,34 @@
+"""
+
+437. Path Sum III
+Medium
+
+Given the root of a binary tree and an integer targetSum, return the number of paths where the sum of the values along the path equals targetSum.
+
+The path does not need to start or end at the root or a leaf, but it must go downwards (i.e., traveling only from parent nodes to child nodes).
+
+ 
+
+Example 1:
+
+
+Input: root = [10,5,-3,3,2,null,11,3,-2,null,1], targetSum = 8
+Output: 3
+Explanation: The paths that sum to 8 are shown.
+Example 2:
+
+Input: root = [5,4,8,11,null,13,4,7,2,null,null,5,1], targetSum = 22
+Output: 3
+ 
+
+Constraints:
+
+The number of nodes in the tree is in the range [0, 1000].
+-109 <= Node.val <= 109
+-1000 <= targetSum <= 1000
+
+"""
+
 # V0 
 # IDEA : BFS + DFS 
 # => USE BFS FIND EVERY NODE IN THE TREE, AND USE DFS GET THR PATH SUM ON EVERY NODE (FOUND BY BFS)
@@ -179,4 +210,4 @@ def pathSumHelper(root, prev, sum):
 
         return pathSumHelper(root, 0, sum) + \
                self.pathSum(root.left, sum) + \
-               self.pathSum(root.right, sum)
+               self.pathSum(root.right, sum)