Why arrays are needed in Go - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of array initialization and access

What is the output of this Go program that initializes an array and prints its elements?

Go

package main
import "fmt"
func main() {
    var arr [3]int = [3]int{10, 20, 30}
    for i := 0; i < len(arr); i++ {
        fmt.Print(arr[i], " ")
    }
}

A 10 20 30

B 10 20 30 0

C 0 0 0

D Compilation error

💡 Hint

Remember arrays hold fixed-size collections of elements of the same type.

The array is initialized with values 10, 20, 30. The loop prints each element separated by space, so output is '10 20 30 '.

🧠 Conceptual

intermediate

Why use arrays instead of separate variables?

Why are arrays useful compared to using many separate variables for similar data?

A Arrays automatically sort the data for you.

B Arrays allow grouping multiple values of the same type under one name for easy management.

C Arrays use less memory than separate variables.

D Arrays can store different types of data in one variable.

💡 Hint

Think about how you handle many similar items in real life, like a row of mailboxes.

Arrays let you keep many values together under one name, making it easier to store, access, and manage related data.

❓ Predict Output

advanced

Output when modifying array elements

What is the output of this Go program that modifies an array element?

Go

package main
import "fmt"
func main() {
    arr := [4]int{1, 2, 3, 4}
    arr[2] = 10
    fmt.Println(arr)
}

A [1 2 10 4]

B [1 2 3 4]

C [10 2 3 4]

D Runtime error

💡 Hint

Arrays allow changing values at specific positions by index.

The element at index 2 (third element) is changed from 3 to 10, so the array prints as [1 2 10 4].

🔧 Debug

advanced

Identify the error in array declaration

What error does this Go code produce and why?

Go

package main
func main() {
    var arr [3]int = [4]int{1, 2, 3, 4}
}

A no error, compiles fine

B index out of range error

C syntax error: missing colon

D cannot use [4]int literal as [3]int value in assignment

💡 Hint

Check if the array sizes on both sides match.

The variable arr is declared as an array of size 3 but assigned an array literal of size 4, causing a type mismatch error.

🚀 Application

expert

Count how many elements in an array are greater than 5

What is the value of count after running this Go code?

Go

package main
import "fmt"
func main() {
    arr := [5]int{3, 7, 2, 9, 5}
    count := 0
    for _, v := range arr {
        if v > 5 {
            count++
        }
    }
    fmt.Println(count)
}

A 3

B 1

C 2

D 0

💡 Hint

Look at each element and count only those greater than 5.

Only 7 and 9 are greater than 5, so count is 2.