Python recursive boring solution (linear time, and constant space) with simple explanation


  • 1
        # O(n) (linear) time, and O(1) (constant) (assuming the output does not count) space complexity
        def convertBST(self, root):
            def generate_greater_tree(node):
                if not node: return None
                right = generate_greater_tree(node.right)
                self.sum += node.val
                new_node = TreeNode(self.sum)
                new_node.right = right
                new_node.left = generate_greater_tree(node.left)
                return new_node
            self.sum = 0
            return generate_greater_tree(root)
    

    Explanation: General idea is doing a reverse order traversal, and adding to the sum as you go for the creation of the new tree.


  • 0
    M

    Really easy to understand!


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