Hashes

Question 1

How do you create a new hash called my_hash using the literal constructor?

Answer 1

my_hash = { }

Question 2

How do you create a new hash called my_hash using the class constructor?

Answer 2

my_hash = Hash.new

Question 3

How would you retrieve the value “Pluto” in the following hash?

pets = {“cat” => “Maru”, “dog” => “Pluto”}

Answer 3

pets[“dog”]

Question 4

How would you add the key and value pair, “bird” and “Sammy in the following hash?

pets = {“cat” => “Maru”, “dog” => “Pluto”}

Answer 4

pets[“bird”] = “Sammy”

Question 5

How would you reassign the value of the key “dog” from “Pluto” to “Koikoi” in the following hash?

pets = {“cat” => “Maru”, “dog” => “Pluto”}

Answer 5

pets[“dog”] = “Koikoi”

Question 6

What does a symbol look like?

Answer 6

:this_is_what_a_symbol_looks_like

Symbols start with a colon.

Question 7

What is the difference between a string and a symbol?

Answer 7

Strings are mutable while symbols are not. Symbols cannot be modified after being created and will always stay the same size in memory.

Question 8

How do you express the symbol :instructor with a value of “Isaac Newton” in a hash?

Answer 8

{ instructor: “Isaac Newton” }

Question 9

How do you iterate over a hash using an each method?

Answer 9

hash.each do |key, value|
  #your code here
end

Question 10

What would the following code look like?

hash = {key1: “value1”, key2: “value2”}

hash.each do |key, value|
puts “#{key}: #{value}”
end

Answer 10

“key1: value1”

“key2: value2”

Question 11

What value will the following code return?

birthday_kids = {
    "Timmy" => 9, 
    "Sarah" => 6, 
    "Amanda" => 27
}

birthday_kids.collect do |kids_name, age|
age * 7
end

Answer 11

[63, 42, 189]

Question 12

How would you retrieve the string “Jasmine” in the following hash?

school = {
instructors: [“Cadence”, “Melody”, “Lryic”],
dev_team: [“Rose”, “Lily”, “Violet”, “Jasmine”],
students: [“Shelly”, “you”, “Sandy”, “Rocky”]
}

Answer 12

school[:dev_team][3]

Question 13

How would you retrieve the string “you” in the following hash?

school = {
instructors: [“Cadence”, “Melody”, “Lyric”],
dev_team: [“Rose”, “Lily”, “Violet”, “Jasmine”],
students: [“Shelly”, “you”, “Sandy”, “Rocky”]
}

Answer 13

school[:students][1]

Question 14

What value will the following code return?

groceries = {fruit: “Banana”, vegetable: “Broccoli”, dessert: “Cookie”}

groceries.values

Answer 14

[“Banana”, “Broccoli”, “Cookie”]

Question 15

What value will the following code return?

groceries = {fruit: “Banana”, vegetable: “Broccoli”, dessert: “Cookie”}

groceries.keys

Answer 15

[:fruit, :vegetable, :dessert]

Question 16

How would you return the values from the following hash?

groceries = {fruit: “Banana”, vegetable: “Broccoli”, dessert: “Cookie”}

Answer 16

groceries.values

Question 17

How would you return the keys from the following hash?

groceries = {fruit: “Banana”, vegetable: “Broccoli”, dessert: “Cookie”}

Answer 17

groceries.keys

Question 18

What value will the following code return?

alphabetical_order = {c: 100, d: 1}

alphabetical_order.min

Answer 18

[c:, 100]

c is lower than d in alphabetical order

Question 19

How would you return the key with the lowest value in the following hash?

alphabetical_order = {c: 100, d: 1}

Answer 19

alphabetical_order.min

Question 20

What value will the following code return?

groceries = {
  dairy: ["milk", "yogurt", "cheese"],
  vegetable: ["carrots", "broccoli", "cucumbers"],
  meat: ["chicken", "steak", "salmon"],
  grains: ["rice", "pasta"]
}

groceries.values

Answer 20

[[“milk”, “yogurt”, “cheese”], [“carrots”, “broccoli”, “cucumbers”], [“chicken”, “steak”, “salmon”], [“rice”, “pasta”]]

Question 21

What value will the following code return?

groceries = {
  dairy: ["milk", "yogurt", "cheese"],
  vegetable: ["carrots", "broccoli", "cucumbers"],
  meat: ["chicken", "steak", "salmon"],
  grains: ["rice", "pasta"]
}

groceries.values.flatten

Answer 21

[“milk”, “yogurt”, “cheese”, “carrots”, “broccoli”, “cucumbers”, “chicken”, “steak”, “salmon”, “rice”, “pasta”]

Question 22

What value will the following code return?

groceries = {
  dairy: ["milk", "yogurt", "cheese"],
  vegetable: ["carrots", "broccoli", "cucumbers"],
  meat: ["chicken", "steak", "salmon"],
  grains: ["rice", "pasta"]
}

groceries.values.flatten.min

Answer 22

“broccoli”