This week's book giveaway is in the Android forum. We're giving away four copies of Head First Android and have Dawn & David Griffiths on-line! See this thread for details.

Hi everyone. I have a problem and would like some help. I would ask that rather than post the whole solution, you gently nudge me in the right direction as I am trying very hard to learn java Ok, here is the problem. I am working on an assignment for school which involves testing all possible positions on a board of a determined size that a chess queen can occupy without being able to take the other queens. I have the array all set up and can print the board out. The first Queen always starts at [0][0] of the board array. Now, I need to place a queen in the next position and then test to see whether any other queens can take it. My original thoughts were to create 2 arrays that contain the x/y directions of the moves a queen can make ie. xPos = {-1,-1,0,1,1,1,0,-1}; yPos = {0,-1,-1,-1,0,1,1,1}; then use these to step back through the array and test for a 'Q'. This is where I get stuck, how can I utilize this or another solution in a recursive method. That is a condition of the assignment, I must use a recursive method to place and test the queens. If anyone needs any more information from me please ask and thankyou for taking the time to read/reply.

The problem you're working on is a well-known problem called the "N Queens Problem." The best hint I can give you is to go to Google and type in "N Queens". There are a dozen excellent links on the first page. Another hint: try to solve the problem conceptually, before trying to solve it in Java. I.e., don't think in terms of "2-d arrays" first. Think in terms of a real chessboard, and looking and searching. Final hint: many simple solutions to this problem are recursive -- i.e., they will use functions that call themselves.

Note that if two queens are on the same row, they can kill each other. Thus they will all have different X (and Y) coordinates. Your recursive function can look for a place to put a queen in each row (or column).