Array declaration in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of array length and values

What is the output of this Go program?

Go

package main
import "fmt"
func main() {
    var arr [3]int = [3]int{1, 2, 3}
    fmt.Println(len(arr))
    fmt.Println(arr[1])
}

A

3
0

B

3
1

C

3
2

D

2
2

💡 Hint

Remember that len(arr) returns the number of elements, and indexing starts at 0.

The array has 3 elements, so len(arr) is 3. The element at index 1 is the second element, which is 2.

❓ Predict Output

intermediate

Array default values

What will this Go program print?

Go

package main
import "fmt"
func main() {
    var arr [4]int
    fmt.Println(arr[2])
}

A undefined

B 2

C nil

D 0

💡 Hint

Uninitialized int array elements have a default value.

In Go, arrays of int type are initialized with zero values, so arr[2] is 0.

📝 Syntax

advanced

Identify the correct array declaration

Which option correctly declares an array of 5 strings in Go?

A arr := [5]string{}

B var arr [5]string

C var arr []string = make([]string, 5)

D var arr [5] = string{}

💡 Hint

Arrays have fixed size and type in Go, slices are different.

Option B declares a fixed-size array of 5 strings. Option B is invalid syntax because it lacks the type after :=. Option B declares a slice, not an array. Option B has wrong syntax for array type.

❓ Predict Output

advanced

Array initialization and zero values

What is the output of this Go program?

Go

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

A 0

B 2

C runtime error

D 3

💡 Hint

Uninitialized elements in an array get zero values.

The array has 4 elements, only first two initialized. The third element (index 2) is zero by default.

🧠 Conceptual

expert

Array vs Slice declaration difference

Which option correctly describes the difference between arrays and slices in Go?

A Arrays have fixed size known at compile time; slices are dynamic and reference arrays.

B Slices have fixed size; arrays can grow dynamically.

C Arrays and slices are the same in Go, just different names.

D Arrays are pointers to slices internally.

💡 Hint

Think about size and mutability differences.

Arrays have fixed size and store elements directly. Slices are dynamic, can grow, and reference underlying arrays.