debug01.rb

list = {'yvr' => 'Vancouver', 'yba' => 'Banff', 'yyz' => 'Toronto', 'yxx' => 'Abbotsford', 'ybw' => 'Calgary'}

# Why is it returning nil instead of first element of the list above
p list['yvr']

debug02.rb

def average(numbers)
  return nil if numbers.empty? # returns nil if array is empty
  numbers = numbers.reject {|no| no == nil} # removing nil elements from the array
  sum = 0
  numbers.each do |num|
    sum += num.to_f # fixes TypeError when running test with array containing string elements
  end
  sum % numbers.size == 0 ? (sum / numbers.size).to_i : sum / numbers.size # only show decimals if needed
end

## TEST HELPER METHOD
def test_average(array = []) # defaults to an empty array if no argument is sent
  print "avg of #{array.inspect}:"
  result = average(array)
  p result
end

## TEST CODE
test_average([4,5,6]) # => 5
test_average([15,5,10]) # => 10

# Should treat string like number
test_average([15,'5',10]) # => 10

# Should show decimal value
test_average([10, 5]) # => 7.5 instead of just 7

# Watch out! Even tests can have bugs!
test_average([9, 5, 7])

# Empty set should return nil, not throw an error
test_average([]) # => nil

# Non-existent set should return nil
test_average() # => nil

# BONUS: Should ignore nils in the set
test_average([9,6,nil,3]) # => 6

debug03.rb

def sum(list)
  ele_sum = 0
  list.each do |ele|
    ele_sum += ele
  end
  ele_sum
end

list1 = [16,21,31,42,55]

# 1. The following should return 165 instead of an error
puts sum(list1)

# 2. How would you refactor it using an enumerable method other than each? Examples of enumerables: map, select, inject, reject, detect.

def sum_refactored(list)
  list.reduce (:+)
end

puts sum_refactored(list1)

debug04.rb

def char_count(list)
  letters = Hash.new(0) # set default value 0 (instead of nil) so as to be able to use + method at line 4 and fix error
  list.each do |word|
    word.split('').each { |letter| letters[letter] += 1 }
  end
  letters
end

# Why the long face(error)?
# 1. This should return count of each letter in the list

list = ['apples', 'oranges', 'hipsters', 'are', 'same']
puts char_count(list)


# 2. What are the improvements you can do to above code?

def char_count_improved(list)
  letters = Hash.new(0)
  # joined all elements of the array into a string and iterated through each character
  list.join.each_char { |letter| letters[letter] += 1 }
  letters
end

puts char_count_improved(list)

# 3. Benchmarking the two methods

require 'benchmark'
char_count_benchmark = Benchmark.measure {1000.times {char_count(list)}}
char_count_improved_benchmark = Benchmark.measure {1000.times {char_count_improved(list)}}
puts "Result of benchmarking original method:\t#{char_count_benchmark.total.round(3)}"
puts "Result of benchmarking improved method:\t#{char_count_improved_benchmark.total.round(3)}"

error_example.rb

def method1(a)
  method2(a)
end

def method2(a)
  method3(a)
end

def method3(a)
  puts a
end

method1(a)