Slice creation in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a slice of integers named numbers.

Go

numbers := [1]

Drag options to blanks, or click blank then click option'

A[]int{1, 2, 3, 4}

B[4]int{1, 2, 3, 4}

Cmap[int]int{1:2, 3:4}

Dint{1, 2, 3, 4}

Attempts:

3 left

💡 Hint

Common Mistakes

Using array syntax with size instead of slice syntax.

Using map syntax instead of slice.

Omitting the brackets.

In Go, slices are created using []type{values}. Option A correctly creates a slice of integers.

2fill in blank

medium

Complete the code to create an empty slice of strings named words.

Go

var words [1]

Drag options to blanks, or click blank then click option'

Amap[string]string

Bstring

C[]string

D[3]string

Attempts:

3 left

💡 Hint

Common Mistakes

Using array type instead of slice.

Using map type instead of slice.

Declaring as a single string variable.

To declare an empty slice of strings, use var words []string.

3fill in blank

hard

Fix the error in the code to create a slice of floats with length 5.

Go

floats := make([1], 5)

Drag options to blanks, or click blank then click option'

A[]float64

Bmap[float64]int

Cfloat64

D[5]float64

Attempts:

3 left

💡 Hint

Common Mistakes

Using array type instead of slice in make.

Using a single type without brackets.

Using map type instead of slice.

The make function requires a slice type like []float64 to create a slice with length 5.

4fill in blank

hard

Fill both blanks to create a slice of integers with length 3 and capacity 5.

Go

nums := make([1], [2], 5)

Drag options to blanks, or click blank then click option'

A[]int

B3

C5

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using array type instead of slice type.

Swapping length and capacity values.

Using a single type without brackets.

The make function creates a slice with type []int, length 3, and capacity 5.

5fill in blank

hard

Fill all three blanks to create a slice of strings named colors with initial values and print its length.

Go

colors := [1]{"red", "green", "blue"}
fmt.Println(len([2]))
fmt.Println([3][1])

Drag options to blanks, or click blank then click option'

A[]string

Bcolors

Dmap[string]int

Attempts:

3 left

💡 Hint

Common Mistakes

Using map type instead of slice.

Using wrong variable names in print statements.

Omitting brackets in slice creation.

We create a slice of strings with []string{"red", "green", "blue"}. Then we print its length and the second element.

Practice

1. What is a slice in Go programming?

easy

A. A flexible, dynamically-sized list of elements.

B. A fixed-size array that cannot change length.

C. A function that slices strings.

D. A type of map with keys and values.

Solution

1. Step 1: Understand slice definition

   A slice in Go is a data structure that holds a list of elements and can grow or shrink in size.

2. Step 2: Compare with other types

   Unlike arrays, slices are dynamic and flexible, unlike maps or functions.

3. Final Answer:

   A flexible, dynamically-sized list of elements. -> Option A

4. Quick Check:

   Slice = dynamic list [OK]

Hint: Remember: slices can grow, arrays cannot [OK]

Common Mistakes:

• Confusing slices with fixed-size arrays
• Thinking slices are functions
• Mixing slices with maps

2. Which of the following is the correct way to create an empty slice of integers in Go?

easy

A. var s []int

B. s := []int{}

C. s := make([]int, 0)

D. All of the above

Solution

1. Step 1: Review slice creation methods

   In Go, you can create an empty slice by declaring a nil slice, using a slice literal with no elements, or using make with length zero.

2. Step 2: Confirm all options are valid

   All three options create an empty slice of integers correctly.

3. Final Answer:

   All of the above -> Option D

4. Quick Check:

   Empty slice creation = D [OK]

Hint: Empty slices can be made in multiple valid ways [OK]

Common Mistakes:

• Using make with negative length
• Confusing array and slice syntax
• Forgetting to initialize slice before use

3. What will be the output of this Go code?

package main
import "fmt"
func main() {
  s := []int{1, 2, 3}
  s = append(s, 4)
  fmt.Println(s)
}

medium

A. [1 2 3]

B. [1 2 3 4]

C. [4]

D. Compilation error

Solution

1. Step 1: Understand initial slice and append

   The slice s starts with elements 1, 2, 3. The append function adds 4 to the end.

2. Step 2: Print the updated slice

   After append, s contains [1 2 3 4], which is printed.

3. Final Answer:

   [1 2 3 4] -> Option B

4. Quick Check:

   append adds element to slice [OK]

Hint: append adds elements to the end of a slice [OK]

Common Mistakes:

• Expecting append to replace elements
• Thinking append returns a new slice without assignment
• Confusing slice with array syntax

4. Identify the error in this Go code snippet:

package main
func main() {
  s := make([]int, 3)
  s[3] = 10
}

medium

A. Slice s is nil

B. Syntax error in make function

C. Index out of range error at s[3]

D. No error, code runs fine

Solution

1. Step 1: Analyze slice length and indexing

   make([]int, 3) creates a slice with length 3, valid indices are 0, 1, 2.

2. Step 2: Check index used in assignment

   Accessing s[3] is out of range and causes a runtime panic.

3. Final Answer:

   Index out of range error at s[3] -> Option C

4. Quick Check:

   Slice indices start at 0, max index = length-1 [OK]

Hint: Slice indices go from 0 to length-1 only [OK]

Common Mistakes:

• Using index equal to slice length
• Confusing slice length and capacity
• Assuming make creates larger slice than specified

5. Given the code below, what will be the length and capacity of slice s after execution?

package main
import "fmt"
func main() {
  s := make([]int, 2, 5)
  s = append(s, 3, 4, 5)
  fmt.Println(len(s), cap(s))
}

hard

A. 5 5

B. 5 10

C. 7 10

D. 3 5

Solution

1. Step 1: Understand make parameters

   make([]int, 2, 5) creates a slice with length 2 and capacity 5.

2. Step 2: Append three elements

   Appending 3 elements increases length from 2 to 5, capacity remains 5 as it is enough.

3. Final Answer:

   5 5 -> Option A

4. Quick Check:

   Length grows with append, capacity stays if enough [OK]

Hint: Capacity grows only if append exceeds current capacity [OK]

Common Mistakes:

• Assuming capacity doubles automatically
• Confusing length and capacity
• Forgetting append increases length