Golfing basics with Ruby

Want to start golfing ?

Let’s start with a « classic » solution that we could write to solve a CodinGame problem.

# 367 chars
# Auto-generated code below aims at helping you parse
# the standard input according to the problem statement.

persons = gets.to_i
heights = []
ages = []
persons.times do
    age, height = gets.split(" ").collect {|x| x.to_i }
    heights << height
    ages << age
end

# Write an action using puts
# To debug: STDERR.puts "Debug messages..."

puts ages.max, heights.min

• Remove comments

  # 180 chars
  persons = gets.to_i
  heights = []
  ages = []
  persons.times do
    age, height = gets.split(" ").collect {|x| x.to_i }
    heights << height
    ages << age
  end
  puts ages.max, heights.min
  

• Trim spaces

  # 155 chars
  persons=gets.to_i
  heights=[]
  ages=[]
  persons.times do
  age,height=gets.split(" ").collect{|x|x.to_i}
  heights<<height
  ages<<age
  end
  puts ages.max,heights.min
  

• Use only 1 Char variables names

  # 102 chars
  p=gets.to_i
  h=[]
  a=[]
  p.times do
  x,y=gets.split(" ").collect{|x|x.to_i}
  h<<y
  a<<x
  end
  puts a.max,h.min
  

• No need to give parameters by default to the methods (split here)

  # 97 chars
  p=gets.to_i
  h=[]
  a=[]
  p.times do
  x,y=gets.split.collect{|x|x.to_i}
  h<<y
  a<<x
  end
  puts a.max,h.min
  

• When multiple aliases exist for the same function, use the shorter (map vs collect vs each)

  # 93 chars
  p=gets.to_i
  h=[]
  a=[]
  p.times do
  x,y=gets.split.map{|x|x.to_i}
  h<<y
  a<<x
  end
  puts a.max,h.min
  

• Use _1 as block’s parameters (_1 stores the block’s first parameter, _2 stores the second one if using .each_with_index for example, etc)

  # 91 chars
  p=gets.to_i
  h=[]
  a=[]
  p.times do
  x,y=gets.split.map{_1.to_i}
  h<<y
  a<<x
  end
  puts a.max,h.min
  

• Replace simple blocks with the function’s symbol to apply

  # 90 chars
  p=gets.to_i
  h=[]
  a=[]
  p.times do
  x,y=gets.split.map(&:to_i)
  h<<y
  a<<x
  end
  puts a.max,h.min
  

• Replace the do ... end with brackets

  # 86 chars
  p=gets.to_i
  h=[]
  a=[]
  p.times{
  x,y=gets.split.map(&:to_i)
  h<<y
  a<<x
  }
  puts a.max,h.min
  

• Avoid useless line breaks

  # 84 chars
  p=gets.to_i
  h=[]
  a=[]
  p.times{x,y=gets.split.map(&:to_i)
  h<<y
  a<<x}
  puts a.max,h.min
  

• Remove parenthesis at the end of chained functions (on the map here)

  # 83 chars
  p=gets.to_i
  h=[]
  a=[]
  p.times{x,y=gets.split.map &:to_i
  h<<y
  a<<x}
  puts a.max,h.min
  

• Do not assign variables that we’ll use only once

  # 79 chars
  h=[]
  a=[]
  gets.to_i.times{x,y=gets.split.map &:to_i
  h<<y
  a<<x}
  puts a.max,h.min