Introduction

Hello, I’m d000hg, and this is my blog. I’m going to use it to talk about anything I find interesting. That means, in nearly all cases, something related to programming or software development. As well as that, articles and algorithmic problems I write will appear here.

As well as here, you can find me on www.gamedev.net and www.topcoder.com/tc

So for this first post, here is a problem I wrote, in a style similar to those found on TopCoder, USACO, etc. Feel free to post ideas, code, bugs, … If you want to discuss this problem on TopCoder’s forums I’m fine with that, we discuss USACO, SPOJ there after all, but please link back to this post.

I have a fair few problems stored up so expect them every couple of days…

I’m new to blogging so any tips about the way I write, or how my blog is set up, are welcome.

2D Palindromes.

A palindrome is a sequence of letters which is the same no matter which way it is read. For instance HANNAH or ABCBA. A 2-dimensional palindrome extends this idea for a table of letters. A section of a table is 2D-palindromic if each row is a palindrome and each column is also a palindrome. For instance:
ABCDEDCBA
BCDEFEDCB
ABCDEDCBA

Here each row is a 9-letter palindrome, and each row a 3-letter palindrome.

Given a string[] grid, where the ith element is the ith row of a character grid, return the area of the largest 2-D palindromic region within this grid.

Examples:
“ABCDEDCBA”,
“BCDEFEDCB”,
“ABCDEDCBA” The whole region is a 2D palindromic so return 9×3 = 27.

“AAAAAAAAAAAAA”,
“AAAAAAAAABBBB”,
“AAAAAAAAABBBB”,
“AAAAAAAAABBBB” There is a 9×4 palindromic region consisting entirely of ‘A’ characters.

Notes:
grid may have between 1 and 50 entries; each entry may have between 1 and 50 upper-case characters A-Z; all entries in grid are the same length.