Arrays

Question 1

build up multi-dimensional arrays

Answer 1

empty_table = Array.new(3) { Array.new(3) }
#=> [[nil, nil, nil], [nil, nil, nil], [nil, nil, nil]]

Question 2

return the first n elements of an array

Answer 2

arr.take(3) #=> [1, 2, 3]

Question 3

special methods first

Answer 3

arr.first #=> 1

Question 4

special methods last

Answer 4

arr.last #=> 6

Question 5

returning the elements after n elements

Answer 5

arr.drop(3) #=> [4, 5, 6]

Question 6

arr = [1, 2, 3, 4, 5, 6]

arr[2]

Answer 6

=> 3

Question 7

arr = [1, 2, 3, 4, 5, 6]

arr[100]

Answer 7

=> nil

Question 8

arr = [1, 2, 3, 4, 5, 6]

arr[-3]

Answer 8

=> 4

Question 9

arr = [1, 2, 3, 4, 5, 6]

arr[2, 3]

Answer 9

=> [3, 4, 5]

Question 10

arr = [1, 2, 3, 4, 5, 6]

arr[1..4]

Answer 10

=> [2, 3, 4, 5]

Question 11

arr = [1, 2, 3, 4, 5, 6]

arr.at(0)

Answer 11

=> 1

Question 12

arr = [‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’]

arr.fetch(100)

Answer 12

=> IndexError: index 100 outside of array bounds: -6…6

Question 13

arr = [‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’]

arr.fetch(100, “oops”)

Answer 13

=> “oops”

Question 14

arr = [1, 2, 3, 4, 5, 6]

arr.first

Answer 14

=> 1

Question 15

arr = [1, 2, 3, 4, 5, 6]

arr.last

Answer 15

=> 6

Question 16

browsers = [‘Chrome’, ‘Firefox’, ‘Safari’, ‘Opera’, ‘IE’]

browsers.length #=> 5

Answer 16

=> 5

Question 17

browsers = [‘Chrome’, ‘Firefox’, ‘Safari’, ‘Opera’, ‘IE’]

browsers.count

Answer 17

=> 5

Question 18

browsers = [‘Chrome’, ‘Firefox’, ‘Safari’, ‘Opera’, ‘IE’]

browsers.empty?

Answer 18

=> false

Question 19

browsers = [‘Chrome’, ‘Firefox’, ‘Safari’, ‘Opera’, ‘IE’]

browsers.include?(‘Konqueror’)

Answer 19

=> false

Question 20

arr = [1, 2, 3, 4]

arr.push(5)

Answer 20

=> [1, 2, 3, 4, 5]

Question 21

arr = [1, 2, 3, 4]

arr

Answer 21

=> [1, 2, 3, 4, 6]

Question 22

add item to array

Answer 22

use arr.push(5) or arr

Question 23

add a new item to the beginning of an array

Answer 23

arr.unshift(0) #=> [0, 1, 2, 3, 4, 5, 6]

Question 24

[1, 2, 3, 4, 5, 6]

arr.unshift(0)

Answer 24

=> [0, 1, 2, 3, 4, 5, 6]

Question 25

add a new element to an array at any position

Answer 25

arr.insert(3, 'apple') #=> [0, 1, 2, 'apple', 3, 4, 5, 6]

Question 26

[0, 1, 2, 3, 4, 5, 6] | arr.insert(3, 'apple')

Answer 26

#=> [0, 1, 2, 'apple', 3, 4, 5, 6]

Question 27

insert multiple values at once

Answer 27

``` arr.insert(3, 'orange', 'pear', 'grapefruit') #=> [0, 1, 2, "orange", "pear", "grapefruit", "apple", 3, 4, 5, 6] ```

Question 28

[0, 1, 2, 'apple', 3, 4, 5, 6] | arr.insert(3, 'orange', 'pear', 'grapefruit')

Answer 28

#=> [0, 1, 2, "orange", "pear", "grapefruit", "apple", 3, 4, 5, 6]

Question 29

removes the last element in an array and returns it

Answer 29

arr = [1, 2, 3, 4, 5, 6] arr.pop #=> 6 arr #=> [1, 2, 3, 4, 5]

Question 30

arr = [1, 2, 3, 4, 5, 6] | arr.pop

Answer 30

arr #=> [1, 2, 3, 4, 5]

Question 31

retrieve and at the same time remove the first item

Answer 31

arr.shift #=> 1 | arr #=> [2, 3, 4, 5]

Question 32

arr #=> [1, 2, 3, 4, 5] | arr.shift

Answer 32

``` #=> 1 arr #=> [2, 3, 4, 5] ```

Question 33

delete an element at a particular index

Answer 33

arr.delete_at(2) #=> 4 | arr #=> [2, 3, 5]

Question 34

arr #=> [2, 3, 4, 5] | arr.delete_at(2) #=> 4

Answer 34

arr #=> [2, 3, 5]

Question 35

delete a particular element anywhere in an array

Answer 35

arr = [1, 2, 2, 3] | arr.delete(2) #=> [1, 3]

Question 36

arr = [1, 2, 2, 3] | arr.delete(2)

Answer 36

#=> [1, 3]

Question 37

arr = [1, 2, 2, 3] | arr.delete(2)

Answer 37

delete a particular element anywhere in an array | arr.delete(2) #=> [1, 3]

Question 38

remove nil values from an array

Answer 38

arr = ['foo', 0, nil, 'bar', 7, 'baz', nil] arr.compact #=> ['foo', 0, 'bar', 7, 'baz'] arr #=> ['foo', 0, nil, 'bar', 7, 'baz', nil] arr.compact! #=> ['foo', 0, 'bar', 7, 'baz'] arr #=> ['foo', 0, 'bar', 7, 'baz']

Question 39

arr = ['foo', 0, nil, 'bar', 7, 'baz', nil] | arr.compact

Answer 39

#=> ['foo', 0, 'bar', 7, 'baz']

Question 40

arr #=> ['foo', 0, nil, 'bar', 7, 'baz', nil] | arr.compact!

Answer 40

arr #=> ['foo', 0, 'bar', 7, 'baz']

Question 41

remove duplicate elements from an array, non-destructive

Answer 41

arr = [2, 5, 6, 556, 6, 6, 8, 9, 0, 123, 556] arr.uniq #=> [2, 5, 6, 556, 8, 9, 0, 123] arr = [2, 5, 6, 556, 6, 6, 8, 9, 0, 123, 556]

Question 42

arr = [2, 5, 6, 556, 6, 6, 8, 9, 0, 123, 556] | arr.uniq

Answer 42

[2, 5, 6, 556, 8, 9, 0, 123] | non-destructive arr = [2, 5, 6, 556, 6, 6, 8, 9, 0, 123, 556]

Question 43

arr = [2, 5, 6, 556, 6, 6, 8, 9, 0, 123, 556] | arr.uniq!

Answer 43

[2, 5, 6, 556, 8, 9, 0, 123] | destructive arr = [2, 5, 6, 556, 8, 9, 0, 123]

Question 44

remove duplicate elements from an array, destructive

Answer 44

arr = [2, 5, 6, 556, 6, 6, 8, 9, 0, 123, 556] arr.uniq! #=> [2, 5, 6, 556, 8, 9, 0, 123] arr = [2, 5, 6, 556, 8, 9, 0, 123]

Question 45

start at iterating over arrays, http://docs.ruby-lang.org/en/2.0.0/Array.html

Answer 45

start at iterating over arrays,http://docs.ruby-lang.org/en/2.0.0/Array.html