Why Arrays Exist and What Problem They Solve in DSA Go - Test Your Knowledge

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an array of 5 integers in Go.

DSA Go

var numbers [[1]]int

Drag options to blanks, or click blank then click option'

A5

B10

C0

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of square brackets

Forgetting to specify the size of the array

The code declares an array named numbers with space for 5 integers.

2fill in blank

medium

Complete the code to assign the value 10 to the first element of the array.

DSA Go

numbers[[1]] = 10

Drag options to blanks, or click blank then click option'

A1

B5

C0

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 as the first index

Using negative indexes which are invalid

Array indexes start at 0 in Go, so the first element is at index 0.

3fill in blank

hard

Fix the error in the code to print the length of the array.

DSA Go

fmt.Println(len([1]))

Drag options to blanks, or click blank then click option'

Anumbers

Bnumbers()

Clen(numbers)

Dnumbers.len

Attempts:

3 left

💡 Hint

Common Mistakes

Calling the variable as a function

Trying to access length as a property

The len function takes the array variable directly without parentheses.

4fill in blank

hard

Fill both blanks to create a loop that prints all elements of the array.

DSA Go

for [1] := 0; [1] < [2]; [1]++ {
    fmt.Println(numbers[[1]])
}

Drag options to blanks, or click blank then click option'

Ai

Blen(numbers)

Cnumbers

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using the array variable as the loop counter

Using incorrect loop condition

The loop variable i starts at 0 and runs while less than the length of the array.

5fill in blank

hard

Fill all three blanks to create an array, assign values, and print the last element.

DSA Go

var [1] [3]int
[1][0] = 5
[1][1] = 10
[1][2] = 15
fmt.Println([1][[2]])

Drag options to blanks, or click blank then click option'

Anums

B2

C3

Dvalues

Attempts:

3 left

💡 Hint

Common Mistakes

Using index 3 which is out of bounds

Using different variable names inconsistently

The array is named nums. The last element index is 2 (since indexes start at 0). We print nums[2].

Practice

1. Why do arrays exist in programming languages like Go?

easy

A. To perform mathematical calculations faster

B. To store values of different types in a single variable

C. To store multiple values of the same type in a fixed-size sequence

D. To replace all other data structures

Solution

1. Step 1: Understand the purpose of arrays

   Arrays are designed to hold multiple values of the same type together in a fixed-size sequence.

2. Step 2: Compare with other options

   The other options describe features not specific to arrays or are incorrect.

3. Final Answer:

   To store multiple values of the same type in a fixed-size sequence -> Option C

4. Quick Check:

   Arrays = fixed-size same-type storage [OK]

Hint: Arrays hold same-type items in order with fixed size [OK]

Common Mistakes:

• Thinking arrays can store different types together
• Confusing arrays with lists or slices
• Believing arrays perform calculations themselves

2. Which of the following is the correct way to declare an array of 5 integers in Go?

easy

A. var arr [5]int

B. int arr[5]

C. var arr []int = make(5)

D. arr := []int{5}

Solution

1. Step 1: Recall Go array declaration syntax

   In Go, arrays are declared with fixed size: var arr [5]int declares an array of 5 integers.

2. Step 2: Analyze other options

   int arr[5] is invalid C-style syntax in Go. var arr []int = make(5) uses make incorrectly (make is for slices, not arrays). arr := []int{5} declares a slice, not an array.

3. Final Answer:

   var arr [5]int -> Option A

4. Quick Check:

   Array declaration = var arr [size]type [OK]

Hint: Use var name [size]type for arrays in Go [OK]

Common Mistakes:

• Using make() for arrays instead of slices
• Confusing slices with arrays
• Initializing arrays with fewer elements than size without explicit zeros

3. What will be the output of the following Go code?

package main
import "fmt"
func main() {
  var arr [3]int
  arr[0] = 10
  arr[1] = 20
  arr[2] = 30
  fmt.Println(arr)
}

medium

A. [10 20]

B. [10 20 30]

C. [0 0 0]

D. Compilation error

Solution

1. Step 1: Understand array initialization and assignment

   The array of size 3 is declared with default zeros. Then each index is assigned 10, 20, and 30 respectively.

2. Step 2: Print the array

   Printing the array shows all elements in order: [10 20 30].

3. Final Answer:

   [10 20 30] -> Option B

4. Quick Check:

   Array after assignments = [10 20 30] [OK]

Hint: Arrays print all elements in order inside brackets [OK]

Common Mistakes:

• Expecting commas between elements in output
• Thinking unassigned elements remain uninitialized
• Confusing slices and arrays output format

4. Identify the error in this Go code snippet that tries to assign a value to an array element:

package main
func main() {
  var arr [3]int
  arr[3] = 100
}

medium

A. Index out of range error at runtime

B. Compilation error: index 3 out of bounds

C. No error, code runs fine

D. Array size is not declared

Solution

1. Step 1: Check array size and index used

   The array has size 3, so valid indices are 0, 1, and 2. Index 3 is out of bounds.

2. Step 2: Understand Go's bounds checking

   Go performs bounds checking at runtime and panics with an index out of range error on out-of-bounds access.

3. Final Answer:

   Index out of range error at runtime -> Option A

4. Quick Check:

   Array index must be less than size [OK]

Hint: Array indices go from 0 to size-1 only [OK]

Common Mistakes:

• Using index equal to array size
• Expecting runtime error instead of compile error
• Confusing slices with arrays for index bounds

5. You want to store the daily temperatures for a week using an array in Go. Which of the following is the best approach and why?

medium

A. Use a single float64 variable and update it daily

B. Use a slice without fixed size to store temperatures

C. Use a map with string keys for days and float64 values

D. Use an array of size 7 with type float64 to store temperatures

Solution

1. Step 1: Analyze the problem requirements

   We need to store exactly 7 temperature values, one for each day of the week.

2. Step 2: Choose the best data structure

   An array of size 7 with float64 type fits perfectly because the size is fixed and known. Slices or maps add unnecessary overhead here. A single variable cannot hold multiple values.

3. Final Answer:

   Use an array of size 7 with type float64 to store temperatures -> Option D

4. Quick Check:

   Fixed-size data = array best choice [OK]

Hint: Fixed known size? Use array for efficient storage [OK]

Common Mistakes:

• Choosing slices when size is fixed and known
• Using maps when order matters and keys are unnecessary
• Trying to store multiple values in one variable