Array Deletion at End in DSA Python - Execution Trace

Concept Flow - Array Deletion at End

Start with array

↓

Check if array is empty?

Yes→Stop: nothing to delete

No↓

Remove last element

↓

Update array size

↓

Done

This flow shows checking if the array is empty, then removing the last element and updating the size.

Execution Sample

DSA Python

arr = [10, 20, 30, 40]
if len(arr) > 0:
    arr.pop()
print(arr)

Deletes the last element from the array if it is not empty, then prints the updated array.

Execution Table

Step	Operation	Array Before	Array After	Pointer Changes	Visual State
1	Start	[10, 20, 30, 40]	[10, 20, 30, 40]	head -> index 0, tail -> index 3	10 -> 20 -> 30 -> 40 -> null
2	Check if empty	[10, 20, 30, 40]	[10, 20, 30, 40]	tail index 3 valid	10 -> 20 -> 30 -> 40 -> null
3	Remove last element	[10, 20, 30, 40]	[10, 20, 30]	tail moves from index 3 to 2	10 -> 20 -> 30 -> null
4	Update size	[10, 20, 30]	[10, 20, 30]	size = 3	10 -> 20 -> 30 -> null
5	Print array	[10, 20, 30]	[10, 20, 30]	no pointer change	10 -> 20 -> 30 -> null
6	End	[10, 20, 30]	[10, 20, 30]	final state	10 -> 20 -> 30 -> null

💡 Stop after last element removed and array size updated.

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
arr	[10, 20, 30, 40]	[10, 20, 30]	[10, 20, 30]	[10, 20, 30]
size	4	3	3	3
tail index	3	2	2	2

Key Moments - 3 Insights

Why do we check if the array is empty before deleting?

Because deleting from an empty array would cause an error. See execution_table step 2 where we check size before removal.

What happens to the array size after deletion?

The size decreases by one after removing the last element, as shown in execution_table step 4 and variable_tracker for 'size'.

How does the 'tail' pointer change after deletion?

The tail pointer moves one position left to the new last element, shown in execution_table step 3 and variable_tracker 'tail index'.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the array after removing the last element?

A [10, 20, 30]

B [10, 20, 30, 40]

C [20, 30, 40]

D []

💡 Hint

Check the 'Array After' column in step 3 of execution_table.

At which step does the tail pointer move to index 2?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at the 'Pointer Changes' column in execution_table step 3.

If the array was empty at start, what would happen at step 2?

A Remove last element anyway

B Throw error

C Stop deletion, no change

D Add a new element

💡 Hint

Refer to concept_flow and execution_table step 2 about empty array check.

Concept Snapshot

Array Deletion at End:
- Check if array is empty before deleting
- Remove last element using pop()
- Update size and tail pointer
- Resulting array has one less element
- Safe deletion avoids errors on empty array

Full Transcript

This visual trace shows how to delete the last element from an array. First, we check if the array is empty to avoid errors. If not empty, we remove the last element, update the size and tail pointer to reflect the new end of the array. The final array is printed showing the updated state. Key points include checking emptiness, pointer updates, and size decrement.