Mind palace

02-05

589. N-ary Tree Preorder Traversal

01-25

666. Path Sum IV

01-20

101. Symmetric Tree

01-20

108. Convert Sorted Array to Binary Search Tree

01-19

617. Merge Two Binary Trees

01-19

116. Populating Next Right Pointers in Each Node

01-19

117. Populating Next Right Pointers in Each Node II

01-18

572. Subtree of Another Tree

01-18

235. Lowest Common Ancestor of a Binary Search Tree

01-18

113. Path Sum II