Array initialization in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an array of 5 integers.

Go

var numbers [5]int = [1]

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

Aarray{1, 2, 3, 4, 5}

B[5]int(1, 2, 3, 4, 5)

C[]int{1, 2, 3, 4, 5}

D[5]int{1, 2, 3, 4, 5}

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of curly braces for initialization.

Using slice syntax instead of array syntax.

Omitting the size inside the square brackets.

The correct way to initialize an array with values in Go is using the syntax [size]type{values}. Here, [5]int{1, 2, 3, 4, 5} creates an array of 5 integers.

2fill in blank

medium

Complete the code to declare an array of 3 strings with default zero values.

Go

var fruits [1]

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

A[]string

B[3]string

Carray[3]string

Dstring[3]

Attempts:

3 left

💡 Hint

Common Mistakes

Using slice syntax instead of array syntax.

Writing the type before the size.

Using invalid syntax like 'array[3]string'.

To declare an array of 3 strings in Go, use [3]string. This creates an array with 3 elements, each initialized to the zero value for strings (empty string).

3fill in blank

hard

Fix the error in the array initialization syntax.

Go

var primes = [1]int{2, 3, 5, 7, 11}

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

A[5]

B(5)

D{5}

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of square brackets for size.

Omitting the size entirely.

Using curly braces for size.

The correct syntax to initialize an array is [size]type{values}. Here, [5]int{2, 3, 5, 7, 11} creates an array of 5 integers.

4fill in blank

hard

Fill both blanks to create an array of 4 floats initialized with values.

Go

var scores [1] = [2]{98.5, 87.0, 92.3, 88.8}}

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

A[4]float64

B[]float64

C[4]

Dfloat64

Attempts:

3 left

💡 Hint

Common Mistakes

Using slice syntax for the value initialization.

Omitting the size in the value initialization.

Using the type name alone without size in the value.

The declaration var scores [4]float64 = [4]{98.5, 87.0, 92.3, 88.8} is almost correct except the second blank should be [4] to specify the array size before the values. This fully defines an array of 4 float64 values.

5fill in blank

hard

Fill all three blanks to declare and initialize an array of 3 booleans with true, false, true.

Go

var flags [1] = [2][3]

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

A[3]bool

B[3]

C{true, false, true}

D[]bool

Attempts:

3 left

💡 Hint

Common Mistakes

Using slice syntax instead of array syntax.

Omitting the size in the value initialization.

Using parentheses instead of curly braces for values.

The correct declaration is var flags [3]bool = [3]{true, false, true}. The first blank is the type with size, the second blank is the size in square brackets for the value, and the third blank is the list of boolean values inside curly braces.

Practice

1. Which of the following correctly declares an array of 5 integers in Go?

easy

A. var arr int[5]

B. var arr [5]int

C. arr := []int{5}

D. arr := [5]int{1, 2, 3, 4}

Solution

1. Step 1: Understand Go array declaration syntax

   In Go, arrays are declared with the syntax: var name [size]type.

2. Step 2: Check each option

   A: var arr int[5] wrong syntax (type before size). B: arr := []int{5} is a slice, not an array. C: var arr [5]int correct syntax. D: arr := [5]int{1, 2, 3, 4} too few initializers (4 < 5), compilation error.

3. Final Answer:

   var arr [5]int -> Option B

4. Quick Check:

   Array declaration = var arr [5]int [OK]

Hint: Remember: var name [size]type declares an array [OK]

Common Mistakes:

• Confusing slices with arrays
• Using wrong syntax like int[5]
• Missing var keyword for array declaration

2. Which of these is the correct way to initialize an array of 3 strings with values "a", "b", "c" in Go?

easy

A. arr := [3]string{"a", "b", "c"}

B. arr := []string{"a", "b", "c"}

C. var arr [3]string = {"a", "b", "c"}

D. arr := [3]string{"a", "b", c}

Solution

1. Step 1: Identify correct array initialization syntax

   Arrays use [size]type{values} syntax. arr := [3]string{"a", "b", "c"} matches this exactly.

2. Step 2: Check other options for errors

   arr := []string{"a", "b", "c"} is a slice, not an array. var arr [3]string = {"a", "b", "c"} uses invalid initialization with = and braces. arr := [3]string{"a", "b", c} misses quotes around "c" causing syntax error.

3. Final Answer:

   arr := [3]string{"a", "b", "c"} -> Option A

4. Quick Check:

   Array init with values = [3]string{"a", "b", "c"} [OK]

Hint: Use [size]type{values} for array initialization [OK]

Common Mistakes:

• Using slice syntax instead of array
• Missing quotes around string elements
• Incorrect use of = with array literals

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

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

medium

A. [1 2 0 0]

B. [1 2]

C. [0 0 0 0]

D. Compilation error

Solution

1. Step 1: Understand partial array initialization

   When fewer elements are provided than the array size, Go fills remaining elements with zero values.

2. Step 2: Apply to given array

   Array size is 4, initialized with 1 and 2. Remaining two elements become 0 by default.

3. Final Answer:

   [1 2 0 0] -> Option A

4. Quick Check:

   Partial init fills rest with zero [OK]

Hint: Uninitialized array elements default to zero [OK]

Common Mistakes:

• Assuming array length matches initializer length
• Expecting error for fewer initial values
• Confusing slices with arrays

4. Identify the error in this Go array initialization:

var arr [3]int = [3]int{1, 2, 3, 4}

medium

A. No error, code is correct

B. Missing var keyword

C. Incorrect type declaration

D. Array size mismatch with initializer

Solution

1. Step 1: Check array size and initializer length

   Array declared with size 3 but initializer has 4 elements.

2. Step 2: Understand Go array rules

   Go requires initializer length to match array size exactly, else compilation error occurs.

3. Final Answer:

   Array size mismatch with initializer -> Option D

4. Quick Check:

   Initializer length must equal array size [OK]

Hint: Initializer length must match array size exactly [OK]

Common Mistakes:

• Ignoring extra elements in initializer
• Assuming Go auto-expands array size
• Confusing slices with arrays

5. You want to create an array of 5 integers where the first two elements are 10 and 20, and the rest are zeros. Which code snippet correctly achieves this and prints the array?

hard

A. arr := [5]int{10, 20, 30}
fmt.Println(arr)

B. arr := [3]int{10, 20}
fmt.Println(arr)

C. arr := [5]int{10, 20, 0, 0, 0}
fmt.Println(arr)

D. arr := []int{10, 20}
fmt.Println(arr)

Solution

1. Step 1: Understand array initialization with explicit zeros

   To ensure the last three elements are zeros explicitly, include them in the initializer.

2. Step 2: Check each option

   B: arr := [3]int{10, 20} fmt.Println(arr) wrong size 3, not 5. A: arr := [5]int{10, 20, 0, 0, 0} fmt.Println(arr) explicitly sets zeros. C: arr := [5]int{10, 20, 30} fmt.Println(arr) third element 30, not zero. D: arr := []int{10, 20} fmt.Println(arr) is a slice, not array.

3. Step 3: Choose the best explicit solution

   A clearly shows all elements matching the requirement exactly.

4. Final Answer:

   arr := [5]int{10, 20, 0, 0, 0} fmt.Println(arr) -> Option C

5. Quick Check:

   Explicit zeros in initializer = arr := [5]int{10, 20, 0, 0, 0} fmt.Println(arr) [OK]

Hint: Explicitly list zeros to avoid confusion [OK]

Common Mistakes:

• Assuming missing elements are always zero without clarity
• Using slices instead of arrays
• Adding unintended values in initializer