Array Insertion at End in DSA C - Execution Trace

Concept Flow - Array Insertion at End

Check if array is full

No↓

Insert element at last index

↓

Increase size count

↓

Done

Yes↓

Cannot insert, array full

This flow shows checking if there is space, inserting the element at the end, updating size, or stopping if full.

Execution Sample

DSA C

int arr[5] = {1, 2, 3};
int size = 3;
int capacity = 5;
int element = 4;

if (size < capacity) {
  arr[size] = element;
  size++;
}

This code inserts element 4 at the end of array if there is space.

Execution Table

Step	Operation	Array State	Size Before	Size After	Pointer Changes	Visual State
1	Check if size < capacity	[1, 2, 3, _, _]	3	3	size=3, capacity=5	Array has space
2	Insert element 4 at arr[size]	[1, 2, 3, 4, _]	3	4	arr[3] = 4	4 inserted at index 3
3	Increment size	[1, 2, 3, 4, _]	4	4	size++	Size updated to 4
4	End	[1, 2, 3, 4, _]	4	4	-	Insertion complete

💡 Insertion stops after size increments; array not full yet.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
arr	[1, 2, 3, _, _]	[1, 2, 3, _, _]	[1, 2, 3, 4, _]	[1, 2, 3, 4, _]	[1, 2, 3, 4, _]
size	3	3	4	4	4
capacity	5	5	5	5	5
element	4	4	4	4	4

Key Moments - 3 Insights

Why do we check if size < capacity before inserting?

Because arrays have fixed size, we must ensure there is space to insert. See execution_table Step 1 where insertion only proceeds if size (3) is less than capacity (5).

What happens if we forget to increment size after insertion?

The size would not reflect the new element, causing future insertions to overwrite existing data. See execution_table Step 3 where size increments from 3 to 4.

Why is the new element inserted at arr[size] and not arr[size-1]?

Because size points to the next free index. Existing elements occupy indices 0 to size-1. See execution_table Step 2 where element 4 is inserted at index 3 (size before increment).

Visual Quiz - 3 Questions

Look at the execution_table, what is the size after Step 2?

A 2

B 3

C 4

D 5

💡 Hint

Check the 'Size After' column for Step 2 in execution_table.

At which step is the new element actually inserted into the array?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Look at the 'Operation' and 'Visual State' columns in execution_table.

If the array was full (size == capacity), what would happen according to the concept_flow?

A Element is inserted anyway

B Insertion stops with message 'Cannot insert, array full'

C Size is incremented without insertion

D Array size increases automatically

💡 Hint

Refer to the 'Yes' branch in concept_flow ASCII diagram.

Concept Snapshot

Array Insertion at End:
- Check if size < capacity
- Insert element at arr[size]
- Increment size by 1
- Stop if array is full
- Fixed size arrays need capacity check

Full Transcript

This concept shows how to insert an element at the end of an array. First, we check if the array has space by comparing size and capacity. If there is space, we place the new element at the index equal to the current size. Then, we increase the size count by one to reflect the new element. If the array is full, insertion is not possible. This ensures we do not overwrite existing data or go out of bounds.