ESAAS HW0 Part 1

hw0-part1.rb

# I iterate over ints using inject and pass in an accumulator
# which for the purposes of summing will have to be 0
# each number is added to the accumulator and the final result
# is returned
def sum(ints)
  ints.inject(0) { |sum, i| sum += i }
end

# this was fun, I sort and mutate the ints array to maintain its
# newly sorted state, pop off the last value which will now be
# the max int or default to 0 if nil, then I pop another one off
# defaulting to 0, and add the two values together
def max_2_sum(ints)
  (ints.sort!.pop || 0) + (ints.pop || 0)
end

# this question was weird, _any_ two elements?
# well ok, at first I reused the max_2_sum method thinking 
# if it can be any 2 i'll pick those since i already have 
# that method handy, so I originally wrote the method as a
# one liner like this:
# ints.size > 1 && max_2_sum(ints.uniq) == n
# but the test failed after I uploaded, so I realized I have 
# to check every int to see if any of them do equal n. So I,
# iterate over ints by creating an enumerator and mapping over it
# getting the index of another int, adding to current int, doing the
# equality checking to build up an array of answers, then finally 
# checking if the result array contained a true value
def sum_to_n?(ints, n)
  return false if ints.size < 2

  ints.each_with_index.map do |i, x|
    other_index = x + 1
    other_int = ints[other_index == ints.size ? 0 : other_index]
    i + other_int == n
  end.any?
end