Common array operations in C++ - Step-by-Step Execution

Concept Flow - Common array operations

Start

↓

Initialize array

↓

Access elements by index

↓

Modify elements

↓

Traverse array with loop

↓

Search for element

↓

Insert or update elements

↓

End

This flow shows how we start with an array, access and change elements, loop through them, search, and update values.

Execution Sample

C++

#include <iostream>
using namespace std;

int main() {
  int arr[5] = {10, 20, 30, 40, 50};
  arr[2] = 35;
  for(int i = 0; i < 5; i++) {
    cout << arr[i] << " ";
  }
  return 0;
}

This code creates an array, changes one element, then prints all elements.

Execution Table

Step	Operation	Index/Variable	Value/Action	Array State	Output
1	Initialize array	-	{10, 20, 30, 40, 50}	{10, 20, 30, 40, 50}
2	Modify element	arr[2]	35	{10, 20, 35, 40, 50}
3	Loop start	i=0	-	{10, 20, 35, 40, 50}
4	Print element	arr[0]	10	{10, 20, 35, 40, 50}	10
5	Increment i	i=1	-	{10, 20, 35, 40, 50}	10
6	Print element	arr[1]	20	{10, 20, 35, 40, 50}	10 20
7	Increment i	i=2	-	{10, 20, 35, 40, 50}	10 20
8	Print element	arr[2]	35	{10, 20, 35, 40, 50}	10 20 35
9	Increment i	i=3	-	{10, 20, 35, 40, 50}	10 20 35
10	Print element	arr[3]	40	{10, 20, 35, 40, 50}	10 20 35 40
11	Increment i	i=4	-	{10, 20, 35, 40, 50}	10 20 35 40
12	Print element	arr[4]	50	{10, 20, 35, 40, 50}	10 20 35 40 50
13	Increment i	i=5	-	{10, 20, 35, 40, 50}	10 20 35 40 50
14	Check loop condition	i < 5	False	{10, 20, 35, 40, 50}	10 20 35 40 50

💡 Loop ends when i reaches 5, condition i < 5 is False

Variable Tracker

Variable	Start	After Step 2	After Step 5	After Step 7	After Step 9	After Step 11	Final
arr	{10,20,30,40,50}	{10,20,35,40,50}	{10,20,35,40,50}	{10,20,35,40,50}	{10,20,35,40,50}	{10,20,35,40,50}	{10,20,35,40,50}
i	-	-	1	2	3	4	5

Key Moments - 3 Insights

Why does arr[2] change from 30 to 35?

Because at step 2 we assign arr[2] = 35, which updates the third element in the array as shown in the execution_table row 2.

Why does the loop stop after i reaches 5?

At step 14, the condition i < 5 becomes False, so the loop ends. This is shown clearly in the execution_table row 14.

Why do we start counting i from 0 in the loop?

Arrays in C++ start at index 0, so to access all elements from first to last, we loop i from 0 up to 4 (less than 5). This is shown in the loop steps 3 to 13.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of arr[2] after step 2?

A 30

B 20

C 35

D 40

💡 Hint

Check the 'Modify element' operation at step 2 in the execution_table.

At which step does the loop condition become false?

A Step 14

B Step 13

C Step 12

D Step 11

💡 Hint

Look at the 'Check loop condition' row in the execution_table.

If we changed the loop to i < 3, how many elements would be printed?

A 2

B 3

C 5

D 4

💡 Hint

Refer to the variable_tracker for i values and loop condition in execution_table.

Concept Snapshot

Common array operations in C++:
- Declare: int arr[5] = {10,20,30,40,50};
- Access: arr[index], index starts at 0
- Modify: arr[2] = 35;
- Loop: for(int i=0; i<5; i++) to traverse
- Arrays have fixed size
- Index out of bounds causes errors

Full Transcript

This visual trace shows common array operations in C++. We start by creating an array with 5 elements. Then we change the third element from 30 to 35. Next, we use a for loop to print all elements from index 0 to 4. The loop stops when the index reaches 5 because the condition i < 5 becomes false. Variables like the array and loop index change step by step, which is tracked in the tables. This helps beginners see exactly how arrays work in C++.