Given a 49x49 grid of numbers, can you place mines in the cells in such a way that each number represents the number of mines in its 3x3 sub-grid (the cell itself and its 8 immediate neighbors)? Find the maximum number of mines that could end up in the middle row of the grid.

Intrigued? Think you can solve it with a clever algorithm? Here at Google, we know how thrilling it can be to encounter a challenge and then overcome it by coding up a creative solution. Since 2003, we've been privileged to share that experience with a global community of computer programmers through our annual programming competition, Google Code Jam.

We're excited to announce Google Code Jam 2009, powered by Google App Engine. Join the fun and compete in several 2½-hour online rounds, attacking three to four difficult algorithmic problems during each round. You may use your favorite programming languages and tools to code up a solution. When ready, run your solution against our fiendish test data. The algorithm needs to be right, and it needs to be efficient: when N=10000, O(N3) won't cut it!

If you're up to the challenge, visit the Google Code Jam site to register and read the rules. Most importantly, you can practice on the problems from last year's contest, so you are in shape when the qualification round starts on September 2. You could be one of the top 25 competitors who will be flown to our Mountain View headquarters to match wits for the $5,000 first prize, and the title of Code Jam champion!

P.S. Think you can solve our "Mine Layer" problem? Try it out on the Code Jam website!