Question

include using namespace std; int main() { int j; int one[5]; int two[10]; for (j = 0; j < 5; j++) one[j] = 5 * j… # What is the output of the following program? #include using namespace std; int main() { int j; int one[5]; int two[10]; for (j = 0; j < 5; j++) one[j] = 5 * j + 3; cout << "One contains: "; for (j = 0; j < 5; j++) cout << one[j] << " "; cout << endl; for (j = 0; j < 5; j++) { two[j] = 2 * one[j] - 1; two[j + 5] = one[4 - j] + two[j]; } cout << "Two contains: "; for (j = 0; j < 10; j++) cout << two[j] << " "; cout << endl; return 0; }

Short answer

The output is: One contains: 3 8 13 18 23 Two contains: 5 15 25 35 45 28 48 58 68 48

Step-by-step solution

Initialize and Fill Array 'one'

The program initializes an array `one` with 5 elements. A `for` loop runs with `j` from 0 to 4, and each element of the array `one` is set to the value `5 * j + 3`. This results in `one` containing the values `[3, 8, 13, 18, 23]`.

Displaying Contents of 'one'

The program uses a `for` loop to iterate through the array `one` and outputs each of its elements. As a result, it prints `One contains: 3 8 13 18 23`.

Initialize and Fill Array 'two' with Two Parts

The program initializes the array `two` with 10 elements. It fills this array in two parts in a loop that iterates with `j` from 0 to 4. The first 5 elements of `two` are filled according to `two[j] = 2 * one[j] - 1`. Calculating for each value in `one`, `two` will be: `[5, 15, 25, 35, 45]`. The next 5 elements are then filled as `two[j + 5] = one[4 - j] + two[j]`, resulting in `two` becoming `[5, 15, 25, 35, 45, 28, 48, 58, 68, 48]`.

Displaying Contents of 'two'

Finally, a `for` loop prints out all the 10 elements of the array `two`. It prints `Two contains: 5 15 25 35 45 28 48 58 68 48`.

Key concepts

C++ Loop Structures

In C++, loop structures are essential for repeated execution of a block of code. The most common loop types are `for`, `while`, and `do-while` loops. In the given exercise, the `for` loop is utilized to manipulate array elements efficiently. A `for` loop consists of three parts: initialization, condition, and increment.

• **Initialization:** It sets a starting point, often initializing a counter variable. For example, `j = 0` in this code.
• **Condition:** It determines if the loop should continue, e.g., `j < 5` ensures the loop runs only for valid array indices.
• **Increment:** It updates the counter variable, like `j++`, to progress through the loop iterations.

The `for` loop in the example fills and manipulates arrays efficiently through defined start and end conditions. Understanding loop control is critical as it ensures we iterate over data structures correctly without over-indexing or under-indexing arrays.

Array Manipulation

Array manipulation in C++ is powerful yet straightforward. It involves accessing, modifying, and processing elements within an array. Arrays are fixed-size sequences, making them ideal for storing and handling collections of data.
In this exercise, two arrays `one` and `two` are manipulated. Here's how:

• **Initialization:** The array `one` is filled with values calculated as `5 * j + 3`. This linear arithmetic operation results in a predictable sequence.
• **Processing:** Array `two` is filled in two stages. The first half is directly calculated from `one` using `two[j] = 2 * one[j] - 1` which performs element-wise processing. The second half uses a combination of reverse indexing from `one` and existing `two` values. This exemplifies manipulating data based on pre-existing results.

Through such manipulations, array data become reusable and adaptable, laying the foundation for more complex data structures and algorithms.

Programming Logic

The essence of any effective program lies in its logic. Programming logic combines algorithms and control structures to solve problems. In the exercise, several programming concepts come together to perform complex operations on two arrays.
Key elements of the logic here include:

• **Sequential Processing:** First, `one` is filled, then displayed. This logical sequence ensures data is ready before it is used elsewhere.
• **Conditional Processing:** The loops execute under specific conditions, ensuring operations happen only within valid array bounds.
• **Reverse Indexing:** The line `one[4 - j] + two[j]` combines forward and backward indexing, demonstrating advanced access patterns within loops.

By understanding this programming logic, you can write code that is both efficient and effective, reusing results of operations like filling arrays dynamically. Mastering these logic patterns is crucial for building scalable and maintainable programs.