Array Deletion at Middle Index in DSA Go - Build from Scratch

Array Deletion at Middle Index

📖 Scenario: You have a list of daily temperatures recorded over a week. Sometimes, a wrong temperature is recorded in the middle of the list. You want to remove that wrong temperature from the list.

🎯 Goal: Build a Go program that removes the middle temperature from the list and prints the updated list.

📋 What You'll Learn

Create an array of 7 integers representing temperatures.

Calculate the middle index of the array.

Remove the element at the middle index.

Print the updated array after removal.

💡 Why This Matters

🌍 Real World

Removing incorrect or unwanted data points from a list of measurements is common in data cleaning.

💼 Career

Understanding how to manipulate arrays and slices is essential for software developers working with data processing.

1

Create the temperature array

Create an array called temps with these exact integer values: 23, 25, 22, 30, 24, 26, 28

DSA Go

# Create the array temps with the given values
# Your code here

Hint

Use Go array syntax with exact values inside curly braces.

2

Calculate the middle index

Add a variable called mid that stores the middle index of the temps array. Use the length of temps divided by 2.

DSA Go

package main

import "fmt"

func main() {
    temps := [7]int{23, 25, 22, 30, 24, 26, 28}
    // Calculate the middle index
    // Your code here
}

Hint

Use len(temps) to get the length and divide by 2.

3

Remove the middle element

Create a slice called updatedTemps that contains all elements of temps except the one at index mid. Use slicing and append to combine the parts before and after mid.

DSA Go

package main

import "fmt"

func main() {
    temps := [7]int{23, 25, 22, 30, 24, 26, 28}
    mid := len(temps) / 2
    // Remove the middle element
    // Your code here
}

Hint

Use append to join slices before and after the middle index.

4

Print the updated array

Print the updatedTemps slice using fmt.Println to show the array after removing the middle element.

DSA Go

package main

import "fmt"

func main() {
    temps := [7]int{23, 25, 22, 30, 24, 26, 28}
    mid := len(temps) / 2
    updatedTemps := append(temps[:mid], temps[mid+1:]...)
    // Print the updatedTemps slice
    // Your code here
}

Hint

Use fmt.Println(updatedTemps) to print the slice.

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