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

Recall & Review

beginner

What does 'Array Insertion at Beginning' mean?

It means adding a new element at the first position (index 0) of an 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 an array?

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

beginner

Show the steps to insert 5 at the beginning of array [10, 20, 30].

Step 1: Shift 30 to index 3<br>Step 2: Shift 20 to index 2<br>Step 3: Shift 10 to index 1<br>Step 4: Insert 5 at index 0<br>Result: [5, 10, 20, 30]

intermediate

What happens if the array is full when inserting at the beginning?

If the array is full, you cannot insert a new element unless you increase the array size or remove an element first.

What is the first step when inserting an element at the beginning of an array?

A Shift all elements one position to the right

B Insert the element at the last position

C Delete the first element

D Replace the first element

To insert at the beginning, all elements must move right to make space.

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

A O(n)

B O(log n)

C O(1)

D O(n^2)

All n elements need to be shifted, so it takes O(n) time.

If an array has elements [1, 2, 3] and we insert 0 at the beginning, what is the new array?

A [1, 2, 3, 0]

B [1, 0, 2, 3]

C [0, 1, 2, 3]

D [0, 1, 3, 2]

The new element 0 is added at the start, shifting others right.

What must be true about the array size to insert a new element at the beginning?

A Array must be full

B Array must have space for one more element

C Array size does not matter

D Array must be empty

There must be space to add a new element; otherwise insertion is not possible.

Which data structure allows easier insertion at the beginning than an array?

A Hash Table

B Stack

C Queue

D Linked List

Linked lists allow insertion at the start without shifting elements.

Explain how to insert an element at the beginning of an array and why shifting elements is necessary.

Think about how arrays store elements in fixed positions.

Describe what happens if you try to insert at the beginning of a full array and how to handle it.

Consider array size and memory limits.