Array Declaration and Initialization in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an array of 5 integers in Go.

DSA Go

var numbers [1]

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

A[5]int

Bint[5]

Carray[5]int

Dint[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'int[5]' which is not valid Go syntax.

Using 'int[]' which is invalid in Go.

Using 'array[5]int' which is not a Go keyword.

In Go, arrays are declared with the size before the type, like [5]int.

2fill in blank

medium

Complete the code to initialize an array with values 1, 2, 3, 4, 5.

DSA Go

numbers := [1]

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

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

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

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

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

Attempts:

3 left

💡 Hint

Common Mistakes

Using slice syntax '[]int{...}' instead of array syntax.

Omitting the type and size in the initialization.

Using just braces without type.

To initialize an array with values in Go, use the syntax [size]type{values}.

3fill in blank

hard

Fix the error in the array declaration to declare an array of 3 strings.

DSA Go

var fruits [1] = {"apple", "banana", "cherry"}

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

Astring[3]

B[]string

Carray[3]string

D[3]string

Attempts:

3 left

💡 Hint

Common Mistakes

Using slice syntax '[]string' when array is needed.

Using 'string[3]' which is invalid syntax.

Using 'array[3]string' which is not a Go keyword.

The correct array declaration in Go uses [3]string with size before type.

4fill in blank

hard

Fill both blanks to declare and initialize an array of 4 floats with values 1.1, 2.2, 3.3, 4.4.

DSA Go

var decimals [1] = [2]

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

A[4]float64

B[4]float32

C[4]float64{1.1, 2.2, 3.3, 4.4}

D[]float64{1.1, 2.2, 3.3, 4.4}

Attempts:

3 left

💡 Hint

Common Mistakes

Using slice initialization syntax '[]float64{...}' for an array.

Using float32 instead of float64 when float64 is expected.

Mismatching declaration and initialization types.

The declaration uses [4]float64 and initialization uses [4]float64{...}.

5fill in blank

hard

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

DSA Go

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

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

A[3]bool

B[3]bool{true, false, true}

C2

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong index to update the array element.

Using slice syntax instead of array syntax.

Mismatching declaration and initialization types.

The array is declared as [3]bool, initialized with [3]bool{true, false, true}, and index 1 is updated to false.

Practice

1. Which of the following is the correct way to declare an array of 5 integers in Go?

easy

A. var arr []int = make([]int, 5)

B. var arr [5]int

C. arr := [5]int

D. arr := []int{5}

Solution

1. Step 1: Understand array declaration syntax in Go

   Arrays in Go are declared with a fixed size inside square brackets, followed by the type, e.g., var arr [5]int.

2. Step 2: Analyze each option

   var arr [5]int correctly declares an array of 5 integers. arr := [5]int uses shorthand but lacks the array literal {}, causing a syntax error. var arr []int = make([]int, 5) declares a slice, not an array. arr := []int{5} declares a slice with one element 5, not an array of size 5.

3. Final Answer:

   var arr [5]int -> Option B

4. Quick Check:

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

Hint: Arrays use fixed size in brackets, slices do not [OK]

Common Mistakes:

• Confusing slices with arrays
• Using shorthand without initialization
• Incorrect size placement

2. Which of the following is the correct syntax to initialize an array with values 1, 2, 3 in Go?

easy

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

B. arr := [3]int(1, 2, 3)

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

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

Solution

1. Step 1: Review array initialization syntax

   In Go, arrays are initialized with curly braces and values inside, e.g., [3]int{1, 2, 3}.

2. Step 2: Check each option

   var arr = [3]int{1, 2, 3} uses correct syntax. arr := [3]int(1, 2, 3) uses parentheses which is invalid. var arr [3]int = {1, 2, 3} misses the type keyword before braces. arr := []int{1, 2, 3} declares a slice, not an array.

3. Final Answer:

   var arr = [3]int{1, 2, 3} -> Option D

4. Quick Check:

   Array init with braces = var arr = [3]int{1, 2, 3} [OK]

Hint: Use curly braces {} for array initialization [OK]

Common Mistakes:

• Using parentheses instead of braces
• Confusing slices with arrays
• Omitting type in declaration

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

package main
import "fmt"
func main() {
  var arr = [4]int{10, 20}
  fmt.Println(arr)
}

medium

A. [10 20 0 0]

B. [10 20]

C. [0 0 0 0]

D. Compilation error

Solution

1. Step 1: Understand partial array initialization

   When an array is partially initialized, the remaining elements are set to zero values (0 for int).

2. Step 2: Analyze the given array

   The array size is 4, but only first two elements are initialized as 10 and 20. The last two elements default to 0.

3. Final Answer:

   [10 20 0 0] -> Option A

4. Quick Check:

   Partial init fills rest with zeros = [10 20 0 0] [OK]

Hint: Uninitialized array elements default to zero [OK]

Common Mistakes:

• Expecting only initialized elements in output
• Thinking partial init causes error
• Confusing slices with arrays

4. Identify the error in the following Go code snippet:

package main
func main() {
  var arr [3]int = [3]int{1, 2}
}

medium

A. No error, code is correct

B. Array size mismatch error

C. Syntax error in array declaration

D. Missing import statement

Solution

1. Step 1: Check array size and initialization

   The array is declared with size 3 but initialized with 2 values. Go allows this and fills the last element with zero.

2. Step 2: Verify syntax and imports

   No syntax error exists. Import is not mandatory if no external packages are used. The code compiles fine.

3. Final Answer:

   No error, code is correct -> Option A

4. Quick Check:

   Partial init allowed, no import needed [OK]

Hint: Partial initialization is allowed; missing imports only if used [OK]

Common Mistakes:

• Assuming size mismatch causes error
• Expecting import for main package
• Confusing slices with arrays

5. You want to declare an array of 5 integers in Go and initialize only the last element to 100, leaving others as zero. Which code snippet achieves this correctly?

hard

A. var arr = [5]int{0: 100}

B. var arr = [5]int{5: 100}

C. var arr = [5]int{4: 100}

D. var arr = [5]int{100}

Solution

1. Step 1: Understand indexed initialization in arrays

   Go allows initializing specific elements by index using syntax like {index: value}. Indexing starts at 0.

2. Step 2: Analyze each option

   var arr = [5]int{4: 100} initializes the element at index 4 (the last element in a 5-element array) to 100, others default to 0. var arr = [5]int{5: 100} uses index 5 which is out of range. var arr = [5]int{100} initializes only the first element. var arr = [5]int{0: 100} initializes index 0 to 100, not the last.

3. Final Answer:

   var arr = [5]int{4: 100} -> Option C

4. Quick Check:

   Use index 4 for last element in 5-size array [OK]

Hint: Index starts at 0; last element is index size-1 [OK]

Common Mistakes:

• Using out-of-range index
• Initializing first element instead of last
• Omitting index for specific element