Array length in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Go code?

Consider the following Go program. What will it print when run?

Go

package main
import "fmt"
func main() {
    arr := [5]int{1, 2, 3, 4, 5}
    fmt.Println(len(arr))
}

A 0

B 5

C 6

D Compilation error

💡 Hint

Remember, len() returns the number of elements in an array.

The array has 5 elements, so len(arr) returns 5.

❓ Predict Output

intermediate

What is the output of this Go code with slice?

What will this Go program print?

Go

package main
import "fmt"
func main() {
    slice := []int{10, 20, 30}
    fmt.Println(len(slice))
}

A Compilation error

B 0

C 3

D Runtime panic

💡 Hint

Slices also have a length accessible by len().

The slice has 3 elements, so len(slice) returns 3.

❓ Predict Output

advanced

What is the output of this Go code with multidimensional array?

What will this program print?

Go

package main
import "fmt"
func main() {
    arr := [2][3]int{{1,2,3},{4,5,6}}
    fmt.Println(len(arr))
    fmt.Println(len(arr[0]))
}

A Compilation error

B 3\n2

C 6\n0

D 2\n3

💡 Hint

len(arr) returns the number of rows, len(arr[0]) returns the number of columns.

The outer array has length 2, each inner array has length 3.

❓ Predict Output

advanced

What error does this Go code produce?

What happens when you run this Go code?

Go

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

A Runtime panic: index out of range

B 0\n0

C Compilation error: invalid array index

D 3\n0

💡 Hint

Accessing arr[3] is out of bounds for an array of length 3.

The program compiles but panics at runtime due to out-of-range index.

🧠 Conceptual

expert

How many elements are in this Go array?

Given this Go array declaration, how many elements does it contain? var arr = [...]int{1, 2, 3, 4, 5, 6, 7}

A 7

B 0

C Compilation error

D Depends on runtime

💡 Hint

The ... tells Go to count the elements automatically.

The ... means Go counts the elements in the initializer, which are 7.