Give an example of an algorithm that is O(1),  an algorithm that is O(n) and an algorithm that is O(n2).  Discuss the difference between them

There are n different sizes of boxes, from 1 to n. There is an unlimited supply of boxes of each size t, each with a value vt . A box of size t can hold several smaller boxes of sizes a1, a2, . . . , ak as long as the sum of sizes a1 + a2 + . . . + ak is strictly less than t. Each of these boxes may be filled with yet more boxes, and so on. Design an algorithm which runs in O(n2 ) time and finds the maximum value that can be attained by taking one box, potentially with smaller boxes nested inside it.

Please provide a correct answer with a full explanation by yourself. Don't copy. Thank you.