Fwd: Ruby Quiz #148

Solution to quiz #148.
Thanks,

-Dave
---------- Forwarded message ----------
From: Dave P. [email protected]
Date: Nov 30, 2007 7:26 PM
Subject: Ruby Q. #148
To: [email protected]

#!/usr/bin/env ruby

op = %w{ + - / * }
pm = %w{ + - }

postfixes = [“2 3 5 + *”,
“1 56 35 + 16 9 - / +”,
“56 34 213.7 + * 678 -”,
“5 9 * 8 7 4 6 + * 2 1 3 * + * + *”]

puts
postfixes.each do |postfix|
stack = []
postfix.split.each do |c|
if op.include?©
second, first = stack.pop, stack.pop
if pm.include?©
stack.push “(#{first} #{c} #{second})”
else
stack.push “#{first} #{c} #{second}”
end
else
stack.push©
end
end
infix = stack.pop
if (infix[0] == 40 && infix[infix.size-1] == 41)
infix = infix[1, infix.size-2]
end
puts “postfix = #{postfix}”
puts “infix = #{infix}”
puts
end

I’ve looked at a lot of solutions for this quiz today and I have to say
I like yours the most. Good work :slight_smile:

On Dec 2, 2007, at 9:17 PM, Michael B. wrote:

I’ve looked at a lot of solutions for this quiz today and I have to
say
I like yours the most. Good work :slight_smile:

Since there was no name specified, I think all solvers should assume
he was talking to you. :wink:

James Edward G. II

On Sun, 02 Dec 2007 21:47:29 -0500, Dave P. wrote:

To: [email protected]
“5 9 * 8 7 4 6 + * 2 1 3 * + * + *”]
stack.push “#{first} #{c} #{second}”
puts “infix = #{infix}”
puts
end

This is incorrect:

postfix = 3 5 * 5 8 * /
infix = 3 * 5 / 5 * 8

It should be
infix = 3 * 5 / (5 * 8)

–Ken

Thanks for pointing that out. I was trying to minimize
parentheses…looks
like i kinda hurried though it. Anyways, here was my first solution
(minus
the bonus points):

#!/usr/bin/env ruby

op = %w{ + - * / }
postfixes = [“2 3 5 + *”,
“1 56 35 + 16 9 - / +”,
“56 34 213.7 + * 678 -”,
“5 9 * 8 7 4 6 + * 2 1 3 * + * + *”,
“3 5 * 5 8 * /”]

postfixes.each do |postfix|
stack = []
postfix.split.each do |c|
unless op.include? c
stack.push©
else
second, first = stack.pop, stack.pop
stack.push “( #{first} #{c} #{second} )”
end
end
puts “postfix = #{postfix}”
puts “infix = #{stack.pop}”
puts
end

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