124. Binary Tree Maximum Path Sum Solution

Author: doh6077

binary-tree-maximum-path-sum/doh6077.py

@@ -0,0 +1,46 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+from collections import deque
+class Solution:
+    def maxPathSum(self, root: Optional[TreeNode]) -> int:
+
+        # # Initially thought I need to use BFS ( misunderstood the question)
+        # if not root:
+        #     return 
+        # queue = deque([root])
+        # result = []
+        # val = 0
+        # max_sum = float('-inf') 
+        # while queue:
+        #     currentNode = queue.popleft()
+        #     result.append(currentNode.val)
+        #     val += currentNode.val
+
+        #     if currentNode.left:
+        #         queue.append(currentNode.left)
+        #         val += currentNode.left.val
+        #     if currentNode.right:
+        #         queue.append(currentNode.right)
+        #         val += currentNode.right.val
+        #     max_sum = max(val, max_sum)
+        #     val = 0
+        # return max_sum
+        res = [root.val]
+
+        def dfs(root):
+            if not root:
+                return 0 
+            leftMax = dfs(root.left)
+            rightMax = dfs(root.right)
+            leftMax = max(leftMax, 0)
+            rightMax = max(rightMax, 0)
+            
+            res[0] = max(res[0], root.val + leftMax + rightMax)
+
+            return root.val + max(leftMax, rightMax)
+        dfs(root)
+        return res[0]