Array Insertion at Middle Index in DSA Python - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output after inserting at the middle index?

Given the array and insertion code below, what is the printed array after insertion?

DSA Python

arr = [10, 20, 30, 40, 50]
mid = len(arr) // 2
arr.insert(mid, 25)
print(arr)

A [10, 20, 25, 30, 40, 50]

B [10, 20, 30, 25, 40, 50]

C [10, 20, 30, 40, 25, 50]

D [25, 10, 20, 30, 40, 50]

💡 Hint

Remember that insert() adds the element before the given index.

The middle index is 2 (5 // 2). Inserting 25 at index 2 places it before the element 30.

❓ Predict Output

intermediate

What is the output after inserting in an even-length array?

What will be printed after inserting 15 at the middle index of the array below?

DSA Python

arr = [5, 10, 20, 25]
mid = len(arr) // 2
arr.insert(mid, 15)
print(arr)

A [5, 10, 15, 20, 25]

B [5, 15, 10, 20, 25]

C [15, 5, 10, 20, 25]

D [5, 10, 20, 15, 25]

💡 Hint

For even length, middle index is length divided by 2.

Length is 4, middle index is 2. Inserting 15 at index 2 places it before 20.

🔧 Debug

advanced

Why does this insertion code raise an error?

Identify the error in the code below and what error it raises.

DSA Python

arr = [1, 2, 3]
mid = len(arr) // 2
arr.insert(mid 4)
print(arr)

A No error, prints [1, 2, 4, 3]

B TypeError because insert() expects only one argument

C IndexError because mid is out of range

D SyntaxError due to missing comma in insert() arguments

💡 Hint

Check the syntax of the insert() method call.

The insert() method requires two arguments separated by a comma. Missing comma causes SyntaxError.

❓ Predict Output

advanced

What is the output after multiple insertions at middle?

What is the final array after these insertions?

DSA Python

arr = [100, 200, 300, 400]
mid = (len(arr) + 1) // 2
arr.insert(mid, 150)
mid = (len(arr) + 1) // 2
arr.insert(mid, 250)
print(arr)

A [100, 150, 200, 250, 300, 400]

B [100, 200, 150, 300, 250, 400]

C [100, 200, 150, 250, 300, 400]

D [150, 100, 200, 250, 300, 400]

💡 Hint

Recalculate middle index after each insertion.

First insertion at index 2 adds 150 before 300. Array becomes [100, 200, 150, 300, 400].

New middle index is 3. Insert 250 at index 3 before 300.

Final array: [100, 200, 150, 250, 300, 400].

🧠 Conceptual

expert

How does insertion at middle index affect time complexity?

Consider an array of size n. What is the time complexity of inserting an element at the middle index?

A O(1) because insertion is direct at the middle index

B O(n) because elements after middle must be shifted

C O(log n) because binary search is used to find middle

D O(n^2) because all elements are copied twice

💡 Hint

Think about what happens to elements after the insertion point.

Inserting in the middle requires shifting all elements after the insertion point one step right, which takes O(n) time.