Array Deletion at Middle Index in DSA Go - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output after deleting middle element from an array

What is the output of the following Go code that deletes the middle element from an array?

DSA Go

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

A [10 20 40 50]

B [10 20 30 40 50]

C [10 20 30 50]

D [20 30 40 50]

💡 Hint

Remember that deleting the middle element means removing the element at index len(arr)/2.

The middle index is 2 (0-based), so element 30 is removed. The resulting array is [10 20 40 50].

❓ Predict Output

intermediate

Result of deleting middle element from even-length array

What is the output of this Go code deleting the middle element from an even-length array?

DSA Go

package main
import "fmt"
func main() {
    arr := []int{5, 10, 15, 20, 25, 30}
    mid := len(arr) / 2
    arr = append(arr[:mid], arr[mid+1:]...)
    fmt.Println(arr)
}

A [5 10 15 20 25 30]

B [5 10 20 25 30]

C [5 10 15 25 30]

D [10 15 20 25 30]

💡 Hint

For even length, middle index is len(arr)/2 which is 3 here.

The middle index is 3, so element 20 is removed. The resulting array is [5 10 15 25 30].

🔧 Debug

advanced

Identify the error in array deletion code

What error does this Go code produce when trying to delete the middle element?

DSA Go

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

A Runtime error: index out of range

B No error, output: [1 2 3 4 5]

C Output: [1 2 3 4 5 3 4 5]

D Output: [1 2 4 5]

💡 Hint

Check the slice indices used in append carefully.

The code appends arr[mid:] instead of arr[mid+1:], so the middle element is not removed. The output is the original array [1 2 3 4 5].

🧠 Conceptual

advanced

Effect of deleting middle element on array length

If you delete the middle element from an array of length n, what will be the length of the resulting array?

A n / 2

B n

C n + 1

D n - 1

💡 Hint

Deleting one element reduces the length by one.

Removing one element from an array reduces its length by exactly one.

🚀 Application

expert

Final array after multiple middle deletions

Starting with array [2, 4, 6, 8, 10, 12, 14], delete the middle element three times in a row. What is the final array?

A [2 4 12 14]

B [2 4 10 12 14]

C [2 6 10 14]

D [2 4 6 8 10 12 14]

💡 Hint

After each deletion, recalculate the middle index for the new array.

Deletions remove elements at indices 3 (8), then 3 (10), then 2 (6), resulting in [2 4 12 14].

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