K Largest Elements

Implement a MinHeap from scratch and use it to extract the k largest
numbers from an unsorted array in O(n log k) time.

MinHeap contract

push(val)   — insert a value and restore the heap invariant
pop()       — remove and return the minimum; null if empty
peek()      — return the minimum without removing; null if empty
size        — getter returning the current element count

Algorithm
Maintain a min-heap of exactly k elements. For each number in nums:

• If the heap has fewer than k items, push unconditionally.
• Otherwise, if the number exceeds the current minimum (peek()), pop

the minimum and push the new number.

After processing all numbers, drain the heap and return the results sorted
in descending order.

Examples

solve([3, 1, 5, 12, 2, 11], 3)   → [12, 11, 5]
solve([7, 7, 7, 7], 2)           → [7, 7]
solve([-4, -1, -7, -3], 2)       → [-1, -3]

Constraints

• 1 ≤ k ≤ nums.length
• Values may be negative or duplicate.
• You must implement the heap manually (no Array.prototype.sort on the

full array — that would be O(n log n) and misses the point).