Array Traversal Patterns in DSA C - Execution Trace

Concept Flow - Array Traversal Patterns

Start at index 0

↓

Check: index < array length?

No→End traversal

Yes↓

Process element at current index

↓

Move to next index (index + 1)

↩Back to Check

Start from the first element, check if index is within bounds, process element, then move to next index until all elements are visited.

Execution Sample

DSA C

int arr[] = {10, 20, 30, 40};
int n = 4;
for (int i = 0; i < n; i++) {
    printf("%d ", arr[i]);
}

Traverse the array from start to end and print each element.

Execution Table

Step	Operation	Index (i)	Condition (i < n)	Element Processed	Output So Far
1	Initialize i=0	0	0 < 4 = True	arr[0] = 10	10
2	Increment i=1	1	1 < 4 = True	arr[1] = 20	10 20
3	Increment i=2	2	2 < 4 = True	arr[2] = 30	10 20 30
4	Increment i=3	3	3 < 4 = True	arr[3] = 40	10 20 30 40
5	Increment i=4	4	4 < 4 = False	None	Traversal ends

💡 Loop ends when index i reaches 4, which is not less than array length 4.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5
i	undefined	0	1	2	3	4
Output	""	"10 "	"10 20 "	"10 20 30 "	"10 20 30 40 "	"Traversal ends"

Key Moments - 3 Insights

Why does the loop stop when i equals the array length, not when i is greater?

Because the condition i < n is checked before processing. When i equals n (array length), the condition becomes false and the loop stops, preventing out-of-bounds access. See execution_table row 5.

What happens if we start i at 1 instead of 0?

The first element arr[0] would be skipped because traversal starts at index 1. The output would miss the first element. This is shown by the initial i value in execution_table row 1.

Why do we increment i after processing the element?

Incrementing i after processing ensures each element is visited exactly once in order. If incremented before processing, the first element would be skipped. The execution_table shows processing happens before increment.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of i at Step 3?

A 3

B 2

C 1

D 4

💡 Hint

Check the 'Index (i)' column at Step 3 in the execution_table.

At which step does the loop condition become false?

A Step 5

B Step 4

C Step 3

D Step 2

💡 Hint

Look at the 'Condition (i < n)' column where it changes to False.

If the array length n was 3 instead of 4, how many elements would be processed?

A 4

B 2

C 3

D 1

💡 Hint

Refer to the condition i < n and how it controls the number of processed elements.

Concept Snapshot

Array Traversal Pattern:
- Start index i at 0
- Loop while i < array length
- Process element at arr[i]
- Increment i by 1 each iteration
- Stops when i reaches array length
Ensures all elements are visited in order.

Full Transcript

Array traversal means visiting each element in an array one by one. We start at index zero and check if the index is less than the array length. If yes, we process the element at that index, then move to the next index by adding one. This repeats until the index reaches the array length, stopping the loop to avoid going outside the array. This pattern ensures every element is accessed safely and in order.