1. Next Greater Element
  2. Next Greater Element - 2
  3. Next Smaller Element
  4. Number of Greater Elements to the Right
  5. Trapping Rainwater
  6. Sum of Subarray Minimums
  7. Asteroid Collision
  8. Sum of Subarray Ranges
  9. Remove K Digits
  10. Largest Rectangle in a Histogram
  11. Maximum Rectangles