Array Deletion at Beginning in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the first element from the slice.

DSA Go

arr := []int{1, 2, 3, 4, 5}
arr = arr[[1]:]
fmt.Println(arr)

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

A1

B0

C2

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 as start index does not remove any element.

Using 2 removes first two elements.

To delete the first element, slice from index 1 to the end.

2fill in blank

medium

Complete the code to print the new length of the slice after deleting the first element.

DSA Go

arr := []int{10, 20, 30, 40}
arr = arr[1:]
fmt.Println(len([1]))

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

Aarr

Barr[1:]

Ccap(arr)

Dlen(arr)

Attempts:

3 left

💡 Hint

Common Mistakes

Using len(arr) before slicing.

Using arr[1:] inside len() gives incorrect length.

After slicing, arr holds the new slice. Use len(arr) to get its length.

3fill in blank

hard

Fix the error in the code to delete the first element and print the updated slice.

DSA Go

arr := []int{5, 6, 7, 8}
arr = arr[[1]]
fmt.Println(arr)

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

A1

B1:

C:1

D0:

Attempts:

3 left

💡 Hint

Common Mistakes

Using arr[1] returns an int, not a slice.

Using arr[:1] returns first element only.

To slice from index 1 to end, use arr[1:]. Using arr[1] accesses a single element, not a slice.

4fill in blank

hard

Complete the code to delete the first two elements and print the updated slice.

DSA Go

arr := []int{9, 8, 7, 6, 5}
arr = arr[[1]:]
fmt.Println(arr)

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

A2

B3

C:

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using arr[:2] slices first two elements, not removes them.

Using arr[3] accesses single element.

To slice from index 2 to end, use arr[2:].

5fill in blank

hard

Fill both blanks to delete the first element, append 100, and print the slice.

DSA Go

arr := []int{1, 2, 3}
arr = arr[[1]:]
arr = append(arr, [2])
fmt.Println(arr)

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

A1

B:

C100

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using arr[0:] does not remove any element.

Appending without slicing keeps old first element.

arr[1:] removes first element. append(arr, 100) adds 100 at the end.

Practice

1. What happens to the array [10, 20, 30, 40] after deleting the first element at the beginning?

easy

A. [40]

B. [10, 20, 30]

C. [20, 30, 40]

D. [30, 40]

Solution

1. Step 1: Understand deletion at beginning

   Deleting the first element removes the element at index 0, which is 10.

2. Step 2: Shift remaining elements left

   The remaining elements 20, 30, 40 shift left to fill the gap, resulting in [20, 30, 40].

3. Final Answer:

   [20, 30, 40] -> Option C

4. Quick Check:

   Remove first element = [20, 30, 40] [OK]

Hint: Remove first element, shift left, rest remain [OK]

Common Mistakes:

• Removing last element instead of first
• Not shifting elements left after deletion
• Leaving the first element in place

2. Which of the following Go code snippets correctly deletes the first element from a slice arr?

easy

A. arr = append(arr, 0)

B. arr = arr[1:]

C. arr = arr[:len(arr)-1]

D. arr = arr[0:]

Solution

1. Step 1: Understand slice slicing syntax

   In Go, arr[1:] creates a slice from index 1 to end, effectively removing the first element.

2. Step 2: Check other options

   arr[:len(arr)-1] removes last element, append(arr, 0) adds element, arr[0:] returns full slice.

3. Final Answer:

   arr = arr[1:] -> Option B

4. Quick Check:

   Slice from index 1 removes first element [OK]

Hint: Use arr = arr[1:] to drop first element [OK]

Common Mistakes:

• Using arr[:len(arr)-1] deletes last element
• Appending instead of slicing
• Using arr[0:] which does not delete anything

3. What is the output of the following Go code?

arr := []int{5, 10, 15, 20}
arr = arr[1:]
fmt.Println(arr)

medium

A. [5 10 15 20]

B. []

C. [15 20]

D. [10 15 20]

Solution

1. Step 1: Initial array elements

   arr starts as [5, 10, 15, 20].

2. Step 2: Slice from index 1

   arr = arr[1:] removes first element 5, resulting in [10, 15, 20].

3. Final Answer:

   [10 15 20] -> Option D

4. Quick Check:

   arr[1:] drops first element [OK]

Hint: arr[1:] slices from second element onward [OK]

Common Mistakes:

• Printing original array without slicing
• Confusing arr[:1] with arr[1:]
• Expecting output with commas instead of spaces

4. The following Go code tries to delete the first element from arr. What is the error?

arr := []int{1, 2, 3, 4}
arr = arr[0:len(arr)]
fmt.Println(arr)

medium

A. No deletion happens; array remains unchanged

B. Syntax error due to incorrect slicing

C. Runtime panic due to out of range slice

D. Deletes last element instead of first

Solution

1. Step 1: Analyze slicing range

   arr[0:len(arr)] returns the full slice unchanged.

2. Step 2: Check effect on array

   Since no elements are removed, arr remains [1, 2, 3, 4].

3. Final Answer:

   No deletion happens; array remains unchanged -> Option A

4. Quick Check:

   Slicing full range keeps array same [OK]

Hint: arr[0:len(arr)] returns full slice, no deletion [OK]

Common Mistakes:

• Assuming slicing deletes first element
• Expecting runtime error from slicing
• Confusing slicing syntax with deletion

5. Given a slice arr := []int{7, 14, 21, 28, 35}, write the Go code to delete the first two elements and print the resulting slice.

hard

A. arr = arr[2:]
fmt.Println(arr)

B. arr = arr[:len(arr)-2]
fmt.Println(arr)

C. arr = arr[1:]
fmt.Println(arr)

D. arr = append(arr[:2], arr[2:]...)
fmt.Println(arr)

Solution

1. Step 1: Understand deletion of first two elements

   To delete first two elements, slice from index 2 to end: arr[2:].

2. Step 2: Verify other options

   arr[:len(arr)-2] removes last two elements, arr[1:] removes only first element, append(arr[:2], arr[2:]...) reconstructs the original slice.

3. Final Answer:

   arr = arr[2:] fmt.Println(arr) -> Option A

4. Quick Check:

   Slice from index 2 removes first two elements [OK]

Hint: Use arr = arr[2:] to remove first two elements [OK]

Common Mistakes:

• Removing last elements instead of first
• Removing only one element instead of two
• Using append unnecessarily for simple slicing