Array initialization in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an array in Go?

An array in Go is a fixed-size collection of elements of the same type stored in contiguous memory locations.

beginner

How do you declare and initialize an array of 3 integers with values 1, 2, and 3 in Go?

You can declare and initialize it like this:

var arr = [3]int{1, 2, 3}

beginner

What happens if you declare an array without initializing it in Go?

The array elements are automatically set to the zero value of the element type. For integers, this is 0.

intermediate

How can you let Go infer the size of an array when initializing it?

Use [...] instead of a fixed size. Example:

arr := [...]int{4, 5, 6}

lets Go count the elements and set the size to 3.

intermediate

Can you initialize an array with some elements and leave others to zero values in Go?

Yes. You can specify values for some indices and the rest will be zero. Example:

arr := [5]int{0: 10, 3: 20}

sets index 0 to 10, index 3 to 20, others to 0.

How do you declare an array of 4 strings in Go with all elements initialized to empty strings?

A var arr []string = {"", "", "", ""}

B var arr [4]string

C arr := [4]string{"", "", "", ""}

D arr := []string{4}

Declaring 'var arr [4]string' creates an array of 4 strings with all elements set to the zero value, which is an empty string.

What does this code do? arr := [...]int{1, 2, 3, 4}

A Declares an array of 4 integers with values 1, 2, 3, 4

B Declares an array of size 3 with values 1, 2, 3

C Declares a slice of 4 integers

D Declares a pointer to an array

The '...' lets Go count the elements and create an array of size 4 with the given values.

What is the zero value of an int array element in Go?

A empty string

B nil

C undefined

D 0

The zero value for int type elements is 0.

How do you initialize only the first and last elements of a 5-element int array in Go?

A arr := [5]int{1, 0, 0, 0, 5}

B arr := [5]int{0: 1, 4: 5}

C Both A and B

D Neither A nor B

Both ways correctly initialize the first and last elements; the rest are zero.

Which of these is NOT a valid way to declare an array in Go?

A var arr []int = [3]int{1, 2, 3}

B arr := [...]int{1, 2, 3}

C arr := [3]int{1, 2, 3}

D var arr [3]int

You cannot assign an array to a slice variable directly without conversion.

Explain how to declare and initialize an array in Go with specific values.

Think about using [size]type{values} or [...]type{values}.

Describe what happens when you declare an array without giving initial values in Go.

Consider what Go sets each element to automatically.