Problem 1
In this problem we simply use the formula that is given in the problem however it may lead to floating point error.Hence we use the formula sum=sum+max(300*x,(1000-4*m[i])*x-50000*w[i]) and divide the final answer by 1000.
Complexity : O(1)
Code : Problem A
Problem 2
In this problem,we first reverse sort the list of sizes and then allocate the k largest sizes to k blocks then we fill the leftover n-k sizes to those k blocks such that largest of n-k pairs with smallest of k boxes and second largest with second smallest and so on.
Complexity : O(nlog(n))
Code : Problem B
You don't need to sort the list in problem 2. The list is already sorted (ascending though). This gives a complexity of O(n).
Any problems with author's editorial? If you wrote another solutions for this problem it would be nice, but your solutions and author solutions are the same. I don't see any reason, why you wrote this blog.