I am searching for an algorithm to fill several slots, which are already filled to some level.

• The current levels and the available quantity to fill are known
• Resulting levels should be as equal as possible, but existing level cannot be reduced
• Slots are filled from left to right, so left slots get higher level if equal level is impossible

The image above shows six examples, each column represents a slot. The grey area is already filled, the blue are is the expected position of the new elements.

I could iterate through my slots and increase the quantity on the lowest slot by 1 until the available quantity is consumed, but I wonder about how to actually calculate the new filling levels.

I am going to implement this with SQL/PL/SQL, other code is just as welcome though :)