Finding an appropriate data structure

Question

I have N keys.

I need to find a data structure which i can do with the following operations :

1. building it in O(N)

2. finding min in O(1)

Answer 1

Simple sorted Array would solve the problem for #2 #3 and #4. But the construction of it would take O(nn). However, there are no restrictions put on space complexity. I am thinking hard to use Hashing concept during the construction of the data structure which would bring down the order to O(n).

Hope this helps. Will get back if I find a better solution