```On 7/13/07, Ruby Quiz <james / grayproductions.net> wrote:
>
> Extra Credit:
>
> Given a matrix of integers, find the rectangle with maximum sum.
>
>
#
# Here is my matrix solution.
# It does the Matrix extra credit.
# If there are multiple rectangles that equal max sum, it prints all of them.
#
# Since the quiz did not specify how to input,
# I just hard coded a sample Matrix at the beginning.
#

require 'matrix'
mat = Matrix[[77,-1,2,3,-4],[-7,8,-22,10,11],[3,15,16,17,-18],[4,22,-23,-24,-25]]
s = []
(0...mat.row_size).each do |a|
(0...mat.column_size).each do |b|
(1..mat.row_size).each do |x|
(1..mat.column_size).each do |y|
s << mat.minor(a,x,b,y)
end
end
end
end

tot = s.uniq.map {|x| x.to_a}
big = tot.max{|x,y| x.flatten.inject(0) {|a,b| a+b} <=>
y.flatten.inject(0) {|c,d| c+d}}
subs = tot.select {|r| r.flatten.inject(0) {|a,b| a+b} ==
big.flatten.inject(0) {|c,d| c+d}}
puts "Original Matrix"
(0...mat.row_size).each do |x|
print mat.row(x).to_a.map{|m| m.to_s.rjust(tot.flatten.max.to_s.length+2)},"\n"
end
puts
puts "Solutions"
subs.each do |x|
puts
x.each {|y| print y.map{|m| m.to_s.rjust(tot.flatten.max.to_s.length+2)},"\n"}
end

# Harry

--
A Look into Japanese Ruby List in English
http://www.kakueki.com/

```