Array limitations in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Go code with arrays?

Consider the following Go program. What will it print?

Go

package main
import "fmt"
func main() {
    var arr [3]int
    fmt.Println(len(arr))
    fmt.Println(cap(arr))
}

A

0
0

B

0
3

C

3
3

D

3
0

💡 Hint

Remember that arrays in Go have fixed size known at compile time.

Arrays in Go have a fixed length. The len function returns the length of the array, which is 3 here. The cap function also returns the capacity, which for arrays is the same as the length.

❓ Predict Output

intermediate

What happens if you assign arrays of different sizes?

What error or output results from this Go code?

Go

package main
func main() {
    var a [3]int
    var b [4]int
    a = b
}

A compile-time error: cannot use b (type [4]int) as type [3]int in assignment

B runtime panic: array size mismatch

C compiles and runs with no output

D compiles but runtime error when assigning

💡 Hint

Arrays of different sizes are different types in Go.

In Go, arrays include their size in their type. You cannot assign an array of size 4 to one of size 3.

🔧 Debug

advanced

Why does this Go code cause an error when passing an array to a function?

Identify the problem in this code and what error it causes.

Go

package main
import "fmt"
func modify(arr [3]int) {
    arr[0] = 100
}
func main() {
    a := [3]int{1,2,3}
    modify(a)
    fmt.Println(a)
}

A Output is [1 2 3] because array is passed by value, so original is unchanged

B Output is [100 2 3] because array is passed by reference

C Compile-time error: cannot assign to array element

D Runtime panic: index out of range

💡 Hint

Think about how arrays are passed to functions in Go.

Arrays are passed by value in Go, so the function modifies a copy. The original array remains unchanged.

🧠 Conceptual

advanced

What is a key limitation of arrays in Go compared to slices?

Choose the best description of a limitation of arrays in Go.

A Arrays can only hold elements of type int

B Arrays have fixed size and cannot be resized after declaration

C Arrays automatically grow when elements are appended

D Arrays support dynamic memory allocation

💡 Hint

Think about what happens if you want to add more elements than the array size.

Arrays in Go have a fixed size set at compile time and cannot be resized. Slices are used for dynamic sizes.

❓ Predict Output

expert

What is the output of this Go code involving array comparison?

What does this program print?

Go

package main
import "fmt"
func main() {
    a := [3]int{1, 2, 3}
    b := [3]int{1, 2, 3}
    c := [3]int{3, 2, 1}
    fmt.Println(a == b)
    fmt.Println(a == c)
}

A

false
true

B

false
false

C

true
true

D

true
false

💡 Hint

Arrays in Go can be compared element-wise if they have the same type and size.

Arrays are equal if all their elements are equal. Here, a and b are equal, a and c are not.