CODEWITHSUNDEEP
ruby
eastafri
eastafri

Reputation: 2226

reading half part of a table

When i have a table;

1 0 0 1 0
0 1 0 1 0
0 0 1 0 1
1 1 1 1 0
0 0 0 0 1

Say i want to only read and keep the values along the upper diagonal of this table, how can i easily accomplish this in pure ruby?

Such that the final structure looks like

1 0 0 1 0
  1 0 1 1 
    1 0 1
      1 0
        1

Thanks

Upvotes: 1

Views: 106

Answers (3)

todb
todb

Reputation: 329

I'm going to assume your table is always square, and the way you create the initial table isn't all that important.

# Create a two-dimensional array, somehow.
table = []
table << %w{1 0 0 1 0} 
table << %w{0 1 0 1 0}
table << %w{0 0 1 0 1}
table << %w{1 1 1 1 0}
table << %w{0 0 0 0 1}

# New table
diagonal = []
table.each_with_index {|x,i| diagonal << x[0,table.size - i]}

# Or go the other direction
diagonal = []
table.each_with_index {|x,i| diagonal << x[0,i+1]}

If you need the values to be integers, then throw a map {|i| i.to_i} in there somewhere.

Upvotes: 1

Jeriko
Jeriko

Reputation: 6637

This assumes you have your table in a file somewhere, but you can basically just drop in from wherever you want to start:

# get data from file
data = File.readlines(path).map(&:chomp)

# convert to array of integers
a = data.map { |line| line.split(" ").map(&:to_i) }

# remove incrementally more elements from each row
a.each_index { |index| a[index].slice!(0,index) }

# alternatively, you could set these to nil
# in order to preserve your row/column structure
a.each_index { |index| index.times { |i| a[index][i] = nil } }

Upvotes: 2

Matthew Flaschen
Matthew Flaschen

Reputation: 284927

input = File.new(filename, "rb")
firstRow = input.readline().split(" ").map  { |el| el.to_i }
len = firstRow.length
table = [firstRow]
remaining = input.readlines().map { |row| row.split(" ").map { |el| el.to_i } }
(len - 1).times  { |i| table << remaining[i].slice(i + 1, len - i - 1) }

Upvotes: 1

Related Questions