Join David Powers for an in-depth discussion in this video Rotating the chessboard, part of Code Clinic: PHP.
- Let's take a look at how we can simulate…rotating the chessboard programmatically.…This is one solution to the eight queens problem…using binary numbers.…Let's remove the zeros to make it easier…to see the bits representing the queens.…When the board is rotated 90 degrees…counterclockwise, the layout looks like this.…The original first row becomes the first column.…The second row becomes the second column,…and so on.…If we look at the original layout on the left,…it should be obvious that there are seven blank…squares below the queen in the first row,…and six in the second row.…
When the board is rotated, the set bit that represents…the queen needs to be shifted left…by the same number of places.…The problem is that the rows are no longer…adjacent to each other.…The queen in what used to be the second row…is now in the fifth row.…So we need to find a way to get the rotated rows…in the correct place.…If we look at the second row in the original layout,…the set bit has been shifted left four places.…In the rotated version it's the same distance…
David introduces challenges and provides an overview of his solutions in PHP. Challenges include topics such as statistical analysis, searching directories for images, and accessing peripheral devices.
Visit other courses in the series to see how to solve the exact same challenges in languages like C#, C++, Java, Python, and Ruby.
Skill Level Intermediate
Q: I'm encountering script errors message with the prime_dates.php file used in the "Priming the date_record column" movie in this course. How can I resolve these errors?
A: To avoid script errors, use bindValue() instead of bindParam() in
Line 9 of the prime_dates.php file. You can also download the latest
copy of the exercise files, which corrects this issue for you. For a
more in-depth explanation of the difference between bindValue() and
bindParam(), check out the "Binding input and output values" video (http://www.lynda.com/PHP-
Q: Why can't I access the Lake Pend Orielle site (http://lpo.dt.navy.mil)?
A: The Lake Pend Orielle site is not accessible in some geographical areas. We have contacted the owner of the server to try to resolve this issue.
Q: I am unable to access the Lake Pend Oreille data from outside the U.S.
A: A static copy of this data is provided here for lynda.com members outside of the U.S
Problem One: Statistical Analysis
Problem Two: Image Analysis
Problem Three: Eight Queens
Problem Four: Accessing Peripherals
Problem Five: Recursion and Directories
Problem Six: Building the Web
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