You've worked through tree and graph problems.
BFS/DFS on grids for connected component counting (Number of Islands)
Topological sort for dependency resolution (Course Schedule)
Dummy node pattern for linked list merge (Merge Two Sorted Lists)
Tree recursion with helper functions (Subtree of Another Tree)
Hash map for node mapping in deep copy (Copy List with Random Pointer)
BFS with direction toggle for zigzag traversal (Binary Tree Zigzag)
Weighted graph + BFS for division queries (Evaluate Division)
Topological sort for recipe dependency chains (Find All Recipes)
Next section covers dynamic programming and design problems.