My solutions to the "Five programming problems every Software Engineer should be able to solve in less than 1 hour"

five_problems.rb

# https://blog.svpino.com/2015/05/07/five-programming-problems-every-software-engineer-should-be-able-to-solve-in-less-than-1-hour
def sum_a(list)
  sum = 0
  for item in list
    sum += item
  end

  return sum
end

def sum_b(list)
  sum = 0
  while !list.empty?
    sum += list.pop
  end

  return sum
end

def sum_c(list)
  return 0 if list.empty?
  sum = list.pop 
  return sum + sum_c(list) 
end

puts sum_a([1, 4, 6, 9, 2])
puts sum_b([1, 4, 6, 9, 2])
puts sum_c([1, 4, 6, 9, 2])

def comb(list_a, list_b)
  ret = []

  max = [list_a.length, list_b.length].max
  max.times do |i|
    ret.push(list_a[i]) if list_a.length > i
    ret.push(list_b[i]) if list_b.length > i
  end

  puts ret.to_s
end

comb([1, 2, 3, 0, 0], [5, 6, 7])

def fib
  fib = [0, 1]
  10.times do |i|
    fib.push(fib[i] + fib[i + 1])
  end

  puts fib.to_s
end

fib

def max_num(list)
  out = ""
  out_data = {}
  list.sort! do |x,y| # In-place sort, with (X, Y) compare function
    x_s = x.to_s # X as a string
    y_s = y.to_s # Y as a string
    x_l = x_s.length # X string length
    y_l = y_s.length # Y string length
    max = [x_l, y_l].max # Longest string

    ret = 0 # Return initialize

    max.times do |i| # for(i = 0; i < max; i++)
      x_i = (x_l > i ? i : 0) # Compare either current number, or the first number if past string limit
      y_i = (y_l > i ? i : 0) # Ditto

      if x_s[x_i] > y_s[y_i] # Handle X > Y case
        ret = -1
        break
      elsif x_s[x_i] < y_s[y_i] # Handle Y > X case
        ret = +1
        break
      end # Default to equal
    end

    ret # Return (X, Y) comparison
  end

  puts list.join(":")
end

max_num([51, 5, 2])
max_num([554, 57, 5])
max_num([2, 5, 51])
max_num([420, 42, 423])

def solve_100
  nums = "1%s2%s3%s4%s5%s6%s7%s8%s9"

  try = [""] * 8
  final = ["-"] * 8
  while try != final
    carry = false

    (0..7).each do |i|
      cur = try[i]
      if cur == "" && (carry || i == 0)
        try[i] = "+"
        carry = false
      elsif cur == "+" && (carry || i == 0)
        try[i] = "-"
        carry = false
      elsif (carry || i == 0)
        try[i] = ""
        carry = true
      end
    end

    to_eval = nums % try
    if eval(to_eval) == 100
      puts to_eval
    end
  end
end

solve_100