# Like a line at a shop. First person in, first person out. # Order of insertion is what matters. # Use collections.deque (not a list) — O(1) on both ends. queue.append(5) # push to back → [5] ...

# each element appears. Returns a dict-like object. # Python has no built-in max-heap. # Trick: negate all values. Push negatives, pop negatives, negate back. nums = [5, 2, 8, 1, 9] max_heap = [-n for ...