Array Deletion at Middle Index in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the element at the middle index from the array.

DSA Go

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

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

A[mid:]

B[mid-1:]

C[mid+1:]

D[mid+2:]

Attempts:

3 left

💡 Hint

Common Mistakes

Using arr[mid:] which includes the middle element again.

Using arr[mid-1:] which removes wrong elements.

To delete the middle element, we keep elements before mid and append elements after mid (mid+1 onwards).

2fill in blank

medium

Complete the code to delete the middle element from the slice and print the updated slice.

DSA Go

nums := []int{10, 20, 30, 40, 50, 60}
mid := len(nums) / 2
nums = append(nums[:mid], nums[1]...)
fmt.Println(nums)

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

A[mid+1:]

B[mid:]

C[mid-1:]

D[:mid]

Attempts:

3 left

💡 Hint

Common Mistakes

Appending nums[mid:] which includes the middle element again.

Using incorrect slice indices causing runtime errors.

To remove the middle element, append elements after mid (mid+1 onwards) to elements before mid.

3fill in blank

hard

Fix the error in the code to correctly remove the middle element from the slice.

DSA Go

values := []int{5, 10, 15, 20, 25}
mid := len(values) / 2
values = append(values[:mid], values[1]...)
fmt.Println(values)

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

A[mid+1:]

B[mid:]

C[mid-1:]

D[:mid]

Attempts:

3 left

💡 Hint

Common Mistakes

Using values[mid:] which does not remove the middle element.

Using values[mid-1:] which removes wrong elements.

The correct slice to append after values[:mid] is values[mid+1:] to exclude the middle element.

4fill in blank

hard

Fill both blanks to remove the middle element from the slice and print the result.

DSA Go

data := []int{2, 4, 6, 8, 10, 12}
mid := len(data) / 2
data = append(data[1], data[2]...)
fmt.Println(data)

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

A[:mid]

B[mid:]

C[mid+1:]

D[:mid+1]

Attempts:

3 left

💡 Hint

Common Mistakes

Using data[mid:] which includes the middle element again.

Using incorrect slice ranges causing wrong output.

Use data[:mid] to get elements before middle and data[mid+1:] to get elements after middle, skipping the middle element.

5fill in blank

hard

Fill all three blanks to remove the middle element from the slice and print the updated slice.

DSA Go

items := []int{7, 14, 21, 28, 35, 42, 49}
mid := len(items) / 2
items = append(items[1], items[2]...)
fmt.Println(items[3])

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

A[:mid]

B[mid+1:]

C[:mid+1]

D[:6]

Attempts:

3 left

💡 Hint

Common Mistakes

Using items[mid:] which includes the middle element again.

Not slicing the printed slice correctly.

Use items[:mid] and items[mid+1:] to remove the middle element. The print slice [:6] shows the updated slice without the removed element.

Practice

1. What happens when you delete the middle element from an array with an odd number of elements?

easy

A. The array size stays the same but the middle element becomes zero.

B. The middle element is removed and the array size decreases by one.

C. The array is reversed after deletion.

D. The first element is removed instead of the middle.

Solution

1. Step 1: Understand array deletion

   Deleting an element removes it and shifts later elements left.

2. Step 2: Effect on array size

   Removing one element reduces the array length by one.

3. Final Answer:

   The middle element is removed and the array size decreases by one. -> Option B

4. Quick Check:

   Delete middle element = size - 1 [OK]

Hint: Deleting removes element and shrinks array size [OK]

Common Mistakes:

• Thinking array size stays the same after deletion
• Assuming deletion replaces element with zero
• Confusing middle deletion with first element deletion

2. Which Go code snippet correctly deletes the middle element from an array named arr with odd length?

easy

A. arr = arr[len(arr)/2+1:]

B. arr = append(arr[1:], arr[:len(arr)-1]...)

C. arr = append(arr[:len(arr)/2], arr[len(arr)/2+1:]...)

D. arr = arr[:len(arr)/2] + arr[len(arr)/2+1:]

Solution

1. Step 1: Identify correct slicing syntax

   In Go, to delete an element at index i, use append(arr[:i], arr[i+1:]...).

2. Step 2: Apply to middle index

   Middle index is len(arr)/2 for odd length, so arr = append(arr[:len(arr)/2], arr[len(arr)/2+1:]...).

3. Final Answer:

   arr = append(arr[:len(arr)/2], arr[len(arr)/2+1:]...) -> Option C

4. Quick Check:

   Use append with slices excluding middle [OK]

Hint: Use append(arr[:i], arr[i+1:]...) to delete index i [OK]

Common Mistakes:

• Using + operator to join slices (invalid in Go)
• Not using ... to expand second slice in append
• Deleting wrong index or slice ranges

3. What is the output of this Go code?

arr := []int{10, 20, 30, 40, 50}
mid := len(arr) / 2
arr = append(arr[:mid], arr[mid+1:]...)
fmt.Println(arr)

medium

A. [10 20 40 50]

B. [10 20 30 40]

C. [20 30 40 50]

D. [10 30 40 50]

Solution

1. Step 1: Calculate middle index

   len(arr) = 5, so mid = 5 / 2 = 2 (integer division).

2. Step 2: Delete element at index 2

   Element at index 2 is 30. After deletion, arr = [10, 20] + [40, 50] = [10 20 40 50].

3. Final Answer:

   [10 20 40 50] -> Option A

4. Quick Check:

   Removed 30 at index 2 [OK]

Hint: Middle index = length/2; remove that element [OK]

Common Mistakes:

• Using float division instead of integer
• Deleting wrong index element
• Not expanding slice with ... in append

4. Find the error in this Go code that tries to delete the middle element from arr:

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

medium

A. The second slice should start from mid+1, not mid.

B. The middle index calculation is wrong.

C. append cannot be used with slices.

D. The array length is even, so no middle element.

Solution

1. Step 1: Check slice ranges in append

   The code uses arr[mid:] which includes the middle element again, not deleting it.

2. Step 2: Correct slice to exclude middle element

   To delete middle element at mid, use arr[mid+1:] to skip it.

3. Final Answer:

   The second slice should start from mid+1, not mid. -> Option A

4. Quick Check:

   Exclude middle element by slicing from mid+1 [OK]

Hint: Second slice must start at mid+1 to delete middle [OK]

Common Mistakes:

• Using arr[mid:] includes middle element again
• Miscalculating middle index for odd length
• Thinking append can't join slices

5. Given an array arr := []int{5, 10, 15, 20, 25, 30, 35}, write the Go code to delete the middle element and then insert 100 at the same middle index. What will be the final array?

hard

A. [5 10 15 20 100 25 30 35]

B. [5 10 15 20 25 30 35 100]

C. [5 10 15 20 25 30 35]

D. [5 10 15 100 25 30 35]

Solution

1. Step 1: Delete middle element

   Length is 7, middle index = 7/2 = 3. Delete element at index 3 (value 20): arr = append(arr[:3], arr[4:]...) = [5 10 15 25 30 35].

2. Step 2: Insert 100 at middle index

   Insert 100 at index 3: arr = append(arr[:3], append([]int{100}, arr[3:]...)...) = [5 10 15 100 25 30 35].

3. Step 3: Verify final array

   Final array is [5 10 15 100 25 30 35].

4. Final Answer:

   [5 10 15 100 25 30 35] -> Option D

5. Quick Check:

   Delete middle, insert 100 at same index [OK]

Hint: Delete middle then insert at same index using append [OK]

Common Mistakes:

• Not updating array after deletion before insertion
• Inserting 100 at wrong index
• Appending 100 at end instead of middle