You've worked through stack, heap, and hash map problems.
Kadane's algorithm for maximum subarray
Greedy scanning with last-occurrence tracking (Partition Labels)
Max-heap for top-k selection (K Closest Points)
Pair stack for min tracking (Min Stack)
Array + hash map for insert/delete/random (Insert Delete GetRandom)
Max-heap + greedy for character rearrangement (Reorganize String)
Floyd's cycle detection on array indices (Find the Duplicate Number)
Stack simulation for collision logic (Asteroid Collision)
Min-heap + frequency map for top-k ordering (Top K Frequent Words)
Next section covers trees and graphs.