Array initialization in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of array initialization with default values

What is the output of this Go program?

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

Go

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

A [0 1 2 3]

B [1 2 3 4]

C [0 0 0 0]

D [4 4 4 4]

💡 Hint

In Go, arrays of integers are initialized with zero values by default.

When you declare an array of integers without assigning values, Go fills it with zeros.

❓ Predict Output

intermediate

Output of array initialization with explicit values

What does this Go program print?

package main
import "fmt"
func main() {
  arr := [3]string{"go", "lang", "rocks"}
  fmt.Println(arr)
}

Go

package main
import "fmt"
func main() {
  arr := [3]string{"go", "lang", "rocks"}
  fmt.Println(arr)
}

A [go lang rocks rocks]

B ["go" "lang" "rocks"]

C [go lang]

D [go lang rocks]

💡 Hint

Arrays print their elements separated by spaces inside square brackets.

The array is initialized with three strings and prints exactly those elements.

❓ Predict Output

advanced

Output of partially initialized array

What is the output of this Go program?

package main
import "fmt"
func main() {
  arr := [5]int{1, 2}
  fmt.Println(arr)
}

Go

package main
import "fmt"
func main() {
  arr := [5]int{1, 2}
  fmt.Println(arr)
}

A [1 2 0 0 0]

B [1 2 3 4 5]

C [0 0 0 0 0]

D [1 2]

💡 Hint

Uninitialized elements in an array get zero values.

Only the first two elements are set; the rest default to zero.

❓ Predict Output

advanced

Output of array initialization with index keys

What does this Go program print?

package main
import "fmt"
func main() {
  arr := [4]int{1: 10, 3: 30}
  fmt.Println(arr)
}

Go

package main
import "fmt"
func main() {
  arr := [4]int{1: 10, 3: 30}
  fmt.Println(arr)
}

A [10 30 0 0]

B [0 10 0 30]

C [1 10 3 30]

D [10 0 30 0]

💡 Hint

Elements not explicitly set get zero values.

Only indexes 1 and 3 are set; others are zero.

🧠 Conceptual

expert

Length of array initialized with ellipsis

What is the length of the array declared in this Go code?

arr := [...]int{5, 10, 15, 20}

Go

package main
import "fmt"
func main() {
  arr := [...]int{5, 10, 15, 20}
  fmt.Println(len(arr))
}

A 4

B 3

C 5

D 0

💡 Hint

The ellipsis lets Go count the elements automatically.

The array length is the number of elements inside the braces.