These problems from [[u:/roadmaps/pattern-22|Pattern ]] test stacks, heaps, and greedy strategies. Solve them before continuing.
Maximum Subarray and Partition Labels test greedy thinking. Amazon asks these because they want to see if you avoid overcomplicating a solution.
K Closest Points to Origin uses a heap for top-k selection. Min Stack pairs each element with the running minimum. Check the walkthroughs if any give you trouble.