Array Insertion at Middle Index in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find the middle index of the array.

DSA Go

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

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

A/

B+

C*

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' instead of '/' causes incorrect index calculation.

Using '*' or '-' will not give the middle index.

The middle index is found by dividing the length of the array by 2 using the '/' operator.

2fill in blank

medium

Complete the code to insert a new element at the middle index of the array.

DSA Go

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

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

Amiddle + 1

Blen(arr)

C0

Dmiddle

Attempts:

3 left

💡 Hint

Common Mistakes

Using len(arr) slices the whole array, causing duplication.

Using 0 inserts at the start, not the middle.

Using middle + 1 inserts after the middle.

We slice the array up to the middle index to insert the new element at that position.

3fill in blank

hard

Fix the error in the code to correctly insert an element at the middle index.

DSA Go

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

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

Amiddle

B0

Cmiddle + 1

Dlen(arr)

Attempts:

3 left

💡 Hint

Common Mistakes

Using middle + 1 causes the new element to be inserted after the middle.

Using 0 or len(arr) slices the wrong part of the array.

The slice should start from the middle index to insert the new element correctly.

4fill in blank

hard

Fill both blanks to create a function that inserts a value at the middle index of an integer slice.

DSA Go

func insertMiddle(arr []int, val int) []int {
	middle := len(arr) [1] 2
	return append(arr[:middle], append([]int{val}, arr[[2]:]...)...)
}

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

A/

B+

Cmiddle

Dlen(arr)

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' instead of '/' for middle calculation.

Slicing from len(arr) instead of middle.

Divide length by 2 to find middle, then slice from middle to insert the value.

5fill in blank

hard

Fill both blanks to insert a value at the middle index and print the updated array.

DSA Go

arr := []int{100, 200, 400, 500}
middle := len(arr) [1] 2
arr = append(arr[:middle], append([]int[2], arr[middle:]...)...)
fmt.Println(arr)

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

A/

B{300}

C:

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' instead of '/' for middle calculation.

Inserting value without curly braces causing type errors.

Using '+' instead of ':' for slicing.

Divide length by 2 for middle, insert {300} at middle, slice arr from middle onwards using ':'.

Practice

1. What is the middle index of an array with 7 elements when inserting a new element?

easy

A. 3

B. 4

C. 2

D. 5

Solution

1. Step 1: Calculate middle index for odd length array

   For an array of length 7, middle index = length / 2 = 7 / 2 = 3 (integer division).

2. Step 2: Confirm insertion position

   The new element should be inserted at index 3 to be in the middle.

3. Final Answer:

   3 -> Option A

4. Quick Check:

   Middle index = 7/2 = 3 [OK]

Hint: Middle index = length divided by 2 (integer division) [OK]

Common Mistakes:

• Using length/2 + 1 for middle index
• Confusing zero-based index with count
• Using length/2 as float instead of integer

2. Which Go code snippet correctly inserts an element `x` at the middle index of slice `arr`?

easy

A. arr = append(arr, x)

B. arr = append(arr[:len(arr)/2], append([]int{x}, arr[len(arr)/2:]...)...)

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

D. arr = append(arr[:len(arr)/2+1], append([]int{x}, arr[len(arr)/2:]...)...)

Solution

1. Step 1: Understand slice insertion in Go

   To insert at middle, split slice at middle index, append new element slice, then append remaining slice.

2. Step 2: Check syntax correctness

   arr = append(arr[:len(arr)/2], append([]int{x}, arr[len(arr)/2:]...)...) correctly uses append with slices and variadic syntax to insert element at middle.

3. Final Answer:

   arr = append(arr[:len(arr)/2], append([]int{x}, arr[len(arr)/2:]...)...) -> Option B

4. Quick Check:

   Correct slice append syntax = arr = append(arr[:len(arr)/2], append([]int{x}, arr[len(arr)/2:]...)...) [OK]

Hint: Use append with slices and variadic ... to insert at middle [OK]

Common Mistakes:

• Trying to append element directly without wrapping in slice
• Incorrect index calculation with +1
• Appending element at end instead of middle

3. What is the output of this Go code?

arr := []int{1, 2, 3, 4}
mid := len(arr) / 2
arr = append(arr[:mid], append([]int{99}, arr[mid:]...)...)
fmt.Println(arr)

medium

A. [1 2 99 3 4]

B. [1 2 3 99 4]

C. [99 1 2 3 4]

D. [1 2 3 4 99]

Solution

1. Step 1: Calculate middle index

   len(arr) = 4, so mid = 4 / 2 = 2.

2. Step 2: Insert 99 at index 2

   arr[:2] = [1, 2], arr[2:] = [3, 4]. Insert 99 between them.

3. Step 3: Resulting array

   New arr = [1, 2, 99, 3, 4]

4. Final Answer:

   [1 2 99 3 4] -> Option A

5. Quick Check:

   Insert 99 at index 2 = [1 2 99 3 4] [OK]

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

Common Mistakes:

• Inserting element at wrong index
• Appending element at end instead of middle
• Misunderstanding slice append syntax

4. Identify the error in this Go code that tries to insert 50 at the middle of slice `nums`:

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

medium

A. Middle index calculation is wrong

B. Slice nums is not initialized

C. Cannot append element and slice together without wrapping element in slice

D. fmt.Println syntax error

Solution

1. Step 1: Check append syntax

   append(nums[:mid], 50, nums[mid:]...) tries to append int and slice variadically, which is invalid.

2. Step 2: Correct approach

   Wrap 50 in a slice: append(nums[:mid], append([]int{50}, nums[mid:]...)...).

3. Final Answer:

   Cannot append element and slice together without wrapping element in slice -> Option C

4. Quick Check:

   Append element + slice needs nested append [OK]

Hint: Wrap single element in slice when appending with another slice [OK]

Common Mistakes:

• Appending element and slice directly together
• Incorrect middle index calculation
• Forgetting variadic ... operator

5. Given a slice `data := []int{5, 10, 15, 20, 25}`, write the correct Go code to insert `100` exactly in the middle, then print the updated slice.

hard

A. mid := len(data)/2
data = append(data[:mid], 100, data[mid:])
fmt.Println(data)

B. mid := len(data)/2
data = append(data[:mid+1], append([]int{100}, data[mid:]...)...)
fmt.Println(data)

C. mid := len(data)/2
data = append(data, 100)
fmt.Println(data)

D. mid := len(data)/2
data = append(data[:mid], append([]int{100}, data[mid:]...)...)
fmt.Println(data)

Solution

1. Step 1: Calculate middle index

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

2. Step 2: Insert 100 at index 2 correctly

   Use nested append: append(data[:mid], append([]int{100}, data[mid:]...)...).

3. Step 3: Print updated slice

   Prints [5 10 100 15 20 25].

4. Final Answer:

   mid := len(data)/2 data = append(data[:mid], append([]int{100}, data[mid:]...)...) fmt.Println(data) -> Option D

5. Quick Check:

   Insert at middle with nested append = mid := len(data)/2 data = append(data[:mid], append([]int{100}, data[mid:]...)...) fmt.Println(data) [OK]

Hint: Use nested append with slices to insert element at middle [OK]

Common Mistakes:

• Using mid+1 instead of mid for insertion
• Appending element at end instead of middle
• Appending element and slice without wrapping element