quiz_answers.rb

# Homework

## Exercise A

### Given the following data structure:

```ruby
stops = [ "Croy", "Cumbernauld", "Falkirk High", "Linlithgow", "Livingston", "Haymarket" ]
```

### Complete these tasks:
Answers are cumulative..?

1. Add `"Edinburgh Waverley"` to the end of the array
  stops << "Edinburgh Waverley"

2. Add `"Glasgow Queen St"` to the start of the array
  stops.unshift("Glasgow Queen St")

3. Add `"Polmont"` at the appropriate point (between `"Falkirk High"` and `"Linlithgow"`)
  stops.insert(4, "Polmont")

4. Work out the index position of `"Linlithgow"`
  linlithgow_index = stops.index("Linlithgow")

5. Remove `"Livingston"` from the array using its name
  stops.delete("Livingston")

6. Delete `"Cumbernauld"` from the array by index
  stops.delete_at(2)

7. How many stops there are in the array?
  stops.length() .size() .count()

8. How many ways can we return `"Falkirk High"` from the array?
  stops[3]
  lin = stops.select{ |a| a == "Falkirk High" }.join
  stops.reject{ |a| a != "Falkirk High" }.join  # .join removes the square brackets
  stops[3...4].join()

9. Reverse the positions of the stops in the array
  stops.reverse()

10. Print out all the stops using a for loop
  for stop in stops
    p stop
  end
## Exercise B

### Given the following data structure:

# ```ruby
users = {
  "Jonathan" => {
    :twitter => "jonnyt",
    :lottery_numbers => [6, 12, 49, 33, 45, 20],
    :home_town => "Stirling",
    :pets => [
    {
      :name => "fluffy",
      :species => "cat"
    },
    {
      :name => "fido",
      :species => "dog"
    },
    {
      :name => "spike",
      :species => "dog"
    }
  ]
  },
  "Erik" => {
    :twitter => "eriksf",
    :lottery_numbers => [18, 34, 8, 11, 24],
    :home_town => "Linlithgow",
    :pets => [
    {
      :name => "nemo",
      :species => "fish"
    },
    {
      :name => "kevin",
      :species => "fish"
    },
    {
      :name => "spike",
      :species => "dog"
    },
    {
      :name => "rupert",
      :species => "parrot"
    }
  ]
  },
  "Avril" => {
    :twitter => "bridgpally",
    :lottery_numbers => [12, 14, 33, 38, 9, 25],
    :home_town => "Dunbar",
    :pets => [
      {
        :name => "monty",
        :species => "snake"
      }
    ]
  }
}
# ```

### Complete these tasks:

1. Get Jonathan's Twitter handle (i.e. the string `"jonnyt"`)
  users["Jonathan"][:twitter]

  # a hash must be followed by [] to access data within

2. Get Erik's hometown
  users["Erik"][:home_town]

3. Get the array of Erik's lottery numbers
  users["Erik"][:lottery_numbers]

4. Get the type of Avril's pet Monty
  p users["Avril"][:pets][0][:species]

  # watch out for bracket types / types of datastructures
  # pets is an array so that it allows us to add more pets (a data group)

5. Get the smallest of Erik's lottery numbers
  users ["Erik"][:lottery_numbers].min()

6. Return an array of Avril's lottery numbers that are even
  users["Avril"][:lottery_numbers].select {|num| num.even?}

    result = []
  for number in users["Avril"][:lottery_numbers]
  	result << number if number.even?
  end
  p result

    Or

  def evil_even_numbers(array_of_numbers)
    result = []
    for number in array_of_numbers
      result.push(number) if(number.even?)
    end

    return result
  end

  array = users["Avril"][:lottery_numbers]
  evens = evil_even_numbers(array)

  p evens

7. Erik is one lottery number short! Add the number `7` to be included in his lottery numbers
  p users["Erik"][:lottery_numbers].push(7)

8. Change Erik's hometown to Edinburgh
  users["Erik"][:home_town] = "Edinburgh"

9. Add a pet dog to Erik called "Fluffy"
  users["Erik"][:pets].push({name: "Fluffy", species: "dog"})

  dog = {                     # alternate method, more readable
  :name => "fluffy",
  :species => "dog"
}

users["Erik"][:pets] << dog

10. Add another person to the users hash
users["Alex"] = {
  :twitter => (),
  :lottery_numbers => [1, 2, 9, 10, 14, 28],
  :home_town => "Edinburgh",
  :pets => [
      {
        :name => (),
        :species => ()
      }
    ]
}

me =  {                       # alternate method, more readable. better for functions?
  :twitter => "tgoncalves",
  :lottery_numbers => [1, 2, 9, 10, 14, 28],
  :home_town => "Morningside",
  :pets => [
      {
        :name => "tommy",
        :species => "cat"
      }
    ]
  }

users["Tony"] = me  # users["Tony"] accesses the user hash and checks if there is a key "Tony", if not, creates new key "Tony"


## Exercise C

### Given the following data structure:

```ruby
united_kingdom = [
  {
    name: "Scotland",
    population: 5295000,
    capital: "Edinburgh"
  },
  {
    name: "Wales",
    population: 3063000,
    capital: "Swansea"
  },
  {
    name: "England",
    population: 53010000,
    capital: "London"
  }
]
```
### Complete these tasks:

1. Change the capital of Wales from `"Swansea"` to `"Cardiff"`.
  united_kingdom[1][:capital] = "Cardiff"

2. Create a Hash for Northern Ireland and add it to the `united_kingdom` array (The capital is Belfast, and the population is 1,811,000).
  united_kingdom.push({name: "Northern Ireland", population: 1811000, capital: "Belfast"})

  northern_ireland = {          # another method, more readable
  name: "Northern Ireland",
  population: 1811000,
  capital: "Belfast"
}
united_kingdom.push(northern_ireland)


3. Use a loop to print the names of all the countries in the UK.
  for country in united_kingdom
    p country[:name]
  end

4. Use a loop to find the total population of the UK.
tot_pop = 0
for country in united_kingdom
  tot_pop += country[:population]
end
p tot_pop