Understand common tree traversals (inorder, preorder, postorder) and algorithms like DFS and BFS.

Trees are a common data structure in competitive programming, and solving tree-related problems requires a good understanding of tree traversals and algorithms like Depth-First Search (DFS) and Breadth-First Search (BFS). Inorder, preorder, and postorder traversals allow you to visit nodes in a specific order, and these techniques are often the basis for solving problems related to binary trees. For more general tree problems, DFS and BFS help in tasks like finding the shortest path, checking for cycles, or determining the depth of the tree. Dynamic programming on trees is also a useful technique for solving optimization problems. Understanding these basic concepts is key to solving tree-related problems efficiently.