problem1.rb

# http://www.softantenna.com/wp/software/5-programming-problems/
# https://blog.svpino.com/2015/05/07/five-programming-problems-every-software-engineer-should-be-able-to-solve-in-less-than-1-hour
#
# 問題1
# forループ、whileループ、および再帰を使用して、リスト内の数字の合計を計算する3つの関数を記述せよ。

@list = [ 1, 7, 3, 12, 5, 8 ].freeze

# @param [Array] list
def funcX(list)
  list.reduce {|result, num|
    result + num
  }
end

# @param [Array] list
def funcX2(list)
  list.reduce(:+)
end

# @param [Array] list
def func1(list)
  result = 0
  for num in list
    result += num
  end
  result
end

# @param [Array] list
def func2(list)
  result = 0
  while !list.empty? do
    result += list.shift
  end
  result
end

# @param [Array] list
def func3(list)
  return 0 if list.empty?
  list.shift + func3(list)
end

p "funcX = #{funcX(@list)}"
p "funcX2 = #{funcX2(@list)}"

p "func1 = #{func1(@list)}"
p "func2 = #{func2(@list.dup)}"
p "func3 = #{func3(@list.dup)}"