Array Insertion at Beginning in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does 'inserting at the beginning of an array' mean?

It means adding a new element at the first position (index 0) of the array, shifting all other elements one position to the right.

beginner

Why do we need to shift elements when inserting at the beginning of an array?

Because arrays have fixed positions, to insert at the start, all existing elements must move one step right to make space for the new element.

intermediate

What is the time complexity of inserting an element at the beginning of a normal array?

The time complexity is O(n), where n is the number of elements, because all elements must be shifted one position to the right.

beginner

Show the array after inserting 5 at the beginning of [10, 20, 30].

The new array will be [5, 10, 20, 30]. The existing elements shift right to make space.

beginner

What Python list method can insert an element at the beginning?

The list method insert(0, value) inserts 'value' at index 0, which is the beginning of the list.

What happens to existing elements when you insert at the beginning of an array?

A They get deleted

B They shift one position to the left

C They stay in the same place

D They shift one position to the right

When inserting at the beginning, all elements move right to make space for the new element.

Which index is used to insert an element at the beginning of a Python list?

A Index 0

B Index 1

C Index -1

D Index length of list

Index 0 is the first position in a list, so inserting at index 0 adds the element at the beginning.

What is the time complexity of inserting at the beginning of an array?

A O(log n)

B O(1)

C O(n)

D O(n^2)

Because all elements must shift, the operation takes linear time proportional to the number of elements.

Which Python list method inserts an element at a specific position?

A append()

B insert()

C extend()

D pop()

The insert() method adds an element at a given index, shifting others as needed.

After inserting 7 at the beginning of [3, 4, 5], what is the new array?

A [7, 3, 4, 5]

B [3, 7, 4, 5]

C [3, 4, 5, 7]

D [4, 5, 7, 3]

Inserting 7 at the start places it at index 0, pushing others right.

Explain step-by-step how to insert an element at the beginning of an array.

Think about moving elements to make space.

Describe the impact on performance when inserting at the beginning of a large array.

Consider how many elements move.