You have learned advanced greedy techniques:
Huffman coding: heap-based tree construction.
Reorganize string: max-heap for frequency balancing.
Remove K digits: stack-based monotonic greedy. In the final section, I will provide practice problems to reinforce all the patterns you have learned. You also learned interval problems (arrows), number construction (create maximum), and range extension (patching). These patterns combine greedy with heap, stack, two-pointer, and mathematical insights. The final section provides practice to reinforce all these techniques together.