How to draw a square grid of size n to console? - ruby

Question

I need to draw a square grid of size n to the console. The grid uses - for horizontal cell boundaries, | for vertical cell boundaries, and + for corners of each cell.
As an example, a size 3 grid should look like the following:
+-+-+-+
| | | |
+-+-+-+
| | | |
+-+-+-+
| | | |
+-+-+-+
I was thinking of using a double for loop with outer loop iterating through rows and inner loop iterating through cols. each iteration of inner loop would be processing an individual cell. drawing | characters doesn't seem to hard but I'm not sure how I'd go about printing the - chars above and below a cell.

Answer 1

You could use Integer#times and String#*:
def print_grid(n)
n.times { print "+-"*n, "+\n", "| "*n, "|\n" }
print "+-"*n, "+\n"
end
print_grid(3)
+-+-+-+
| | | |
+-+-+-+
| | | |
+-+-+-+
| | | |
+-+-+-+
=> nil
Alternatively:
def print_grid(n)
puts n.times.map{ "+-"*n + "+\n" + "| "*n + "|\n" }.join + "+-"*n + "+\n"
end

Answer 2

For a width of 3, you have a separator-row like this:
+-+-+-+
This can be sees as either:
3 - connected by and surrounded by +
4 + connected by -
The latter is a bit easier to express in Ruby:
width = 3
Array.new(width + 1, '+').join('-')
#=> "+-+-+-+"
The same works for the cell-row:
Array.new(width + 1, '|').join(' ')
#=> "| | | |"
Vertically, you have 3 cell-rows connected by and surrounded by separator-rows. (that should ring a bell) Just like before, this can also be expressed as 4 separator-rows connected by cell-rows.
Let's store our separator-row and cell-row in variables: (we also have to append newlines)
width = 3
separator_row = Array.new(width + 1, '+').join('-') << "\n"
cell_row = Array.new(width + 1, '|').join(' ') << "\n"
And define the grid:
height = 3
grid = Array.new(height + 1, separator_row).join(cell_row)
#=> "+-+-+-+\n| | | |\n+-+-+-+\n| | | |\n+-+-+-+\n| | | |\n+-+-+-+\n"
put grid
Output:
+-+-+-+
| | | |
+-+-+-+
| | | |
+-+-+-+
| | | |
+-+-+-+

Answer 3

Here are two ways to do that.
Determine each character depending on whether the row and column indices are even or odd
def grid(n)
sz = 2*n+1
Array.new(sz) do |i|
Array.new(sz) do |j|
if i.even?
j.even? ? '+' : '-'
else # i is odd
j.even? ? '|' : ' '
end
end.join
end
end
puts grid(3)
+-+-+-+
| | | |
+-+-+-+
| | | |
+-+-+-+
| | | |
+-+-+-+
puts grid(4)
+-+-+-+-+
| | | | |
+-+-+-+-+
| | | | |
+-+-+-+-+
| | | | |
+-+-+-+-+
| | | | |
+-+-+-+-+
Use an enumerator
def pr_grid(n)
enum = [*['+','-']*n, "+", "\n", *['|',' ']*n, "|", "\n"].cycle
((2+2*n)*(1+2*n)).times { print enum.next }
end
pr_grid(3)
+-+-+-+
| | | |
+-+-+-+
| | | |
+-+-+-+
| | | |
+-+-+-+
pr_grid(4)
+-+-+-+-+
| | | | |
+-+-+-+-+
| | | | |
+-+-+-+-+
| | | | |
+-+-+-+-+
| | | | |
+-+-+-+-+
For n = 3 the steps are as follows.
a = [*['+','-']*n, "+", "\n", *['|',' ']*n, "|", "\n"]
#=> ["+", "-", "+", "-", "+", "-", "+", "\n",
# "|", " ", "|", " ", "|", " ", "|", "\n"]
enum = a.cycle
#=> #<Enumerator: ["+", "-", "+", "-", "+", "-", "+", "\n",
# "|", " ", "|", " ", "|", " ", "|", "\n"]:cycle
enum.next #=> "+"
enum.next #=> "-"
enum.next #=> "+"
enum.next #=> "-"
enum.next #=> "+"
enum.next #=> "-"
enum.next #=> "+"
enum.next #=> "\n"
enum.next #=> "|"
enum.next #=> " "
and so on.

Answer 4

Just for fun and just as an example, here is a list of methods (to be optimized and debugged and maybe used within a class) that you can use also for filling a table.
#cell = '|'
#line = '-'
#cross = '+'
def build_row(content)
(content.zip [#cell]* content.size).flatten.prepend(#cell).join
end
def separator_from_content(content)
content.map { |e| #line * e.size + #cross }.prepend(#cross).join
end
def adjust_content_in(lines)
width = lines.flatten.max_by(&:size).size
lines.map { |line| line.map { |e| e << ' ' * (width - e.size) } }
end
def build_table(lines)
lines = adjust_content_in(lines)
separator = separator_from_content(lines.first)
mapped = lines.map { |line| build_row(line) }.zip([separator] * (lines.size) )
return mapped.flatten.prepend(separator).join("\n")
end
def empty_squared_table(n)
lines = n.times.map { n.times.map { ' ' } }
build_table(lines)
end
So, if you want to draw an empty table, can call:
n = 3
puts empty_squared_table(n)
# +-+-+-+
# | | | |
# +-+-+-+
# | | | |
# +-+-+-+
# | | | |
# +-+-+-+
Or you can fill in some text (more lines inside a cell not supported):
lines = [['so', 'you can', 'fill'], ['a table', 'given the content', '']]
puts build_table(lines)
# +-----------------+-----------------+-----------------+
# |so |you can |fill |
# +-----------------+-----------------+-----------------+
# |a table |given the content| |
# +-----------------+-----------------+-----------------+