Create Count Nodes Equal to Average of Subtree - Leetcode 2265.py

Author: gahogg

Count Nodes Equal to Average of Subtree - Leetcode 2265.py

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+class Solution:
+    def averageOfSubtree(self, root: TreeNode) -> int:
+        num_nodes = [0]
+
+        def dfs(root):
+            if not root:
+                return (0, 0)
+            
+            N_left, summ_left = dfs(root.left)
+            N_right, summ_right = dfs(root.right)
+
+            N = 1 + N_left + N_right
+            summ = root.val + summ_left + summ_right
+            avg = summ // N
+
+            if root.val == avg:
+                num_nodes[0] += 1
+
+            return (N, summ)
+        
+        dfs(root)
+        return num_nodes[0]
+        # Time: O(N)
+        # Space: O(N)
+        
+