Collections and Control Flow (Arrays, Dictionaries) (if, Switch )

Question 1

What are the 3 collection types in swift?

Answer 1

Array, dictionary and sets

Question 2

When you concatenate two things, what must the have in common?

Answer 2

They must be of the same type. So String and string or [Int] and [Int]

Question 3

Given an array:
let a = [2.0, 1.1, 2.3, 5.4]

What is a’s type?

Answer 3

[Double]

Question 4

let a = [1,2,3]
a.insert(4, at: 3)

The code raises an error. Why?

Answer 4

The array is immutable and cannot be changed

Question 5

let a = [1, 2, 3]
a[3]

The code above crashes. Why?

Answer 5

The index value provided is out of bounds

Question 6

To get the 4th item out of an array, which index number do we use?

Answer 6

3

Question 7

TF: An array preserves the order of its elements, i.e., it is an ordered collection.

Answer 7

True

Question 8

Remove the 5th item in this array.
var a = [10, 1, 12, 22, 96, 14]

Answer 8

a.remove(at: 4)

Question 9

What exactly is a dictionary?

Answer 9

Set of key, value pairs

Question 10

What happens when you try to get a value that does not exist in an array vs dictionary?

Answer 10

Array → it crashes

Dictionary → it will return nil because dictionaries are always of an optional type.

Question 11

Given the following dictionary:
let dict = [1: "someValue", 2: "anotherValue"]

What is the dictionary’s type?

Answer 11

[Int : String]

Question 12

When we try to access a value using a key that doesn’t exist in a dictionary, what result do we get?

Answer 12

A nil value

Question 13

TF: The following code snippets are equivalent
dict.updateValue(“yetAnotherValue”, forKey: 3)
And
dict[3] = “yetAnotherValue”

Answer 13

True

Question 14

TF: A dictionary is an ordered collection and preserves the order of key-value pairs added to it

Answer 14

False

Question 15

What is an if statement?

Answer 15

if statement is a conditional statement that executes some code depending on the conditions stated.

Question 16

If you have a bunch of possibilities in an if else statement, when will the condition be met?

Answer 16

As soon as a condition is satisfied from top to bottom, the code will be executed.

Question 17

Give all the possibilities when using && or ||.

Answer 17

True && True → True
True && False → False
False && False → False 
True || True → True
True || False → True 
False || False → False

Question 18

How does a switch statement work?

Answer 18

Switch (value to consider) {
	case value1: response to value1
	case value1: response to value2
	default : do this
}

Question 19

What's missing from this switch statement? 
let months = 1...12

for month in months {
    switch month {
        case 1:
            print("January")
    }
}

Answer 19

The above code will not compile because switch statements need to be exhaustive with case statements for all expected values or a default statement.

Question 20

var isAvailable = true
var isCheap = true

var status: String

if !isCheap && !isAvailable {
    status = "super rare"
} else if isCheap && isAvailable {
    status = "not rare"
} else if !isCheap && isAvailable {
    status = "somewhat rare"
} else {
    status = "common"
}

What does status evaluate to?

Answer 20

“Not rare”

Question 21

TF: Both the AND and OR operators use short circuit evaluation

Answer 21

True

Question 22

What does the following statement evaluate to?

!true || !false) && (true && !false

Answer 22

True