Problem

Given a stack of n disks, move the disks from the first stack to the last stack, using only three stacks and moving only one disk at a time. The disks must be moved so that the smallest disk is on top of the largest disk.
Input:
3
1
2
3
Output:
1
3
2

Solution

# The optimal solution is to move the smallest disk to the middle stack, then move the largest disk to the last stack, then move the smallest disk to the last stack.
# This is optimal because it is the only way to move the smallest disk to the top of the last stack.