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

Recall & Review

beginner

What happens when you delete the first element of an array?

The first element is removed, and all other elements shift one position to the left to fill the gap.

beginner

Why do we need to shift elements after deleting the first element in an array?

Because arrays have fixed positions, shifting keeps the array continuous without empty spaces.

beginner

Show the array after deleting the first element from [10, 20, 30, 40].

After deletion, the array becomes [20, 30, 40]. The elements 20, 30, and 40 shift left by one position.

intermediate

What is the time complexity of deleting the first element in an array?

It is O(n) because all elements after the first must be shifted one position to the left.

intermediate

Can we delete the first element of an array without shifting elements?

No, because arrays store elements in continuous memory. To keep order, shifting is necessary.

What must be done after deleting the first element of an array?

A Do nothing

B Shift all elements to the left by one position

C Replace the first element with zero

D Shift all elements to the right by one position

After deleting the first element, all other elements must shift left to fill the empty space.

What is the time complexity of deleting the first element in an array of size n?

A O(1)

B O(log n)

C O(n)

D O(n^2)

Deleting the first element requires shifting all other n-1 elements, so time complexity is O(n).

If the array is [5, 10, 15], what is the array after deleting the first element?

A []

B [5, 10, 15]

C [15, 10]

D [10, 15]

The first element 5 is removed, and the rest shift left, resulting in [10, 15].

Why can't we just mark the first element as deleted without shifting?

A Because arrays require continuous memory without gaps

B Because marking is not allowed in arrays

C Because shifting is faster

D Because arrays are linked lists

Arrays store elements in continuous memory, so gaps are not allowed; shifting maintains continuity.

What happens to the size of the array after deleting the first element?

A It decreases by one logically

B It increases by one

C It stays the same

D It doubles

Logically, the array size decreases by one because one element is removed.

Explain step-by-step how to delete the first element of an array and update the array.

Think about what happens to each element after deletion.

Describe the time complexity of deleting the first element in an array and why it is that way.

Consider how many elements move after deletion.