Is the N Queens problem NP-hard? The N-queen problem is this:

Input : N

Output : A placement of N "queens" on an NXN chessboard such that no two queens lie on the same row, column or diagonal.

Doing a google search on this, I found that many slides by many professors claim this is an NP-Hard problem.(eg. web.mst.edu/~ercal/387/slides/NP-Hard.ppt)

However I havent been able to find a proof (or derive one).
The reason I ask this question is because I think I have an algorithm that solves certain instances of the problem i.e. with N not a multiple of 2 or 3 (N is the number of queens)
Related Issue - Can we consider the input size to be N (where N is the number of queens)? Or do we take the input size to be log(N), since the number 'N' can be represented in log(N) bits?
As stated, the answer to this question is NO.

References : 
A polynomial time algorithm http://dl.acm.org/citation.cfm?id=101343 [courtesy: vzn]

Another much simpler technique : http://dl.acm.org/citation.cfm?id=122322 [courtesy: Jeffe]