Question

include using namespace std; int main() { int list1[5]; int list2[15]; for (int i = 0; i < 5; i++) list1[i] = i… # What is the output of the following C++ code? #include using namespace std; int main() { int list1[5]; int list2[15]; for (int i = 0; i < 5; i++) list1[i] = i * i - 2; cout << "list1: "; for (int i = 0; i < 5; i++) cout << list1[i] << " "; cout << endl; for (int i = 0; i < 5; i++) { list2[i] = list1[i] * i; list2[i + 5] = list1[4 - i] + i; list2[i + 10] = list2[9 - i] + list2[i]; } cout << "list2: "; for (int i = 0; i < 7; i++) cout << list2[i] << " "; cout << endl; return 0; }

Short answer

The output is `list1: -2 -1 2 7 14` and `list2: 0 -1 4 21 56 14 8`.

Step-by-step solution

Initialize and Fill list1

The array `list1` of size 5 is initialized. Each element of `list1` is assigned using the formula `i * i - 2`: - When `i=0`, `list1[0]=0*0-2=-2` - When `i=1`, `list1[1]=1*1-2=-1` - When `i=2`, `list1[2]=2*2-2=2` - When `i=3`, `list1[3]=3*3-2=7` - When `i=4`, `list1[4]=4*4-2=14`. The array `list1` thus becomes `{-2, -1, 2, 7, 14}`.

Print list1

The statement `cout << "list1: "` outputs `list1: `, followed by iterating over `list1` using a loop. The loop iterates from `i=0` to `i=4` and prints each element of `list1` separated by spaces, resulting in `-2 -1 2 7 14` being displayed.

Fill list2 with First Set of Values

The array `list2` is of size 15. A loop assigns values based on `list1`: - `list2[i] = list1[i] * i` for `i=0` to `i=4`: - `list2[0] = -2*0 = 0` - `list2[1] = -1*1 = -1` - `list2[2] = 2*2 = 4` - `list2[3] = 7*3 = 21` - `list2[4] = 14*4 = 56`.

Fill list2 with Second Set of Values

Continuation of the loop assigns values to `list2[i+5]`: - `list2[i+5] = list1[4-i] + i` for `i=0` to `i=4`: - `list2[5] = 14 + 0 = 14` - `list2[6] = 7 + 1 = 8` - `list2[7] = 2 + 2 = 4` - `list2[8] = -1 + 3 = 2` - `list2[9] = -2 + 4 = 2`.

Fill list2 with Third Set of Values

Continuation of the loop assigns values to `list2[i+10]`: - `list2[i+10] = list2[9-i] + list2[i]` for `i=0` to `i=4`: - `list2[10] = list2[9] + list2[0] = 2 + 0 = 2` - `list2[11] = list2[8] + list2[1] = 2 - 1 = 1` - `list2[12] = list2[7] + list2[2] = 4 + 4 = 8` - `list2[13] = list2[6] + list2[3] = 8 + 21 = 29` - `list2[14] = list2[5] + list2[4] = 14 + 56 = 70`.

Print list2

The statement `cout << "list2: "` outputs `list2: `, followed by iterating over `list2` for `i=0` to `i=6`. The elements `list2[0]` through `list2[6]` are `0, -1, 4, 21, 56, 14, 8`, which are printed separated by spaces, displaying `list2: 0 -1 4 21 56 14 8`.

Key concepts

C++ for loops

In C++, for loops are a fundamental control structure that allows you to repeat a block of code a certain number of times. They are particularly useful for dealing with arrays, where each element needs to be accessed or modified.

A typical for loop in C++ consists of three main parts:

• Initialization, which sets the starting point of the loop.
• Condition, which determines how long the loop will run.
• Increment/Decrement, which alters the loop variable after each iteration.

Here is the basic syntax of a C++ for loop:

```cpp for (initialization; condition; increment) { // Code to execute } ```
In our example, the loop `for (int i = 0; i < 5; i++)` iterates 5 times. Each iteration manipulates elements in `list1` and `list2` based on a formula. Understanding how for loops operate is crucial for effectively using arrays since they allow you to automate element processing.

array initialization

Array initialization in C++ refers to the process of assigning values to the elements of an array when it is declared or shortly thereafter.

When dealing with arrays, it is vital to understand how they store data. Arrays allocate memory space to hold a fixed number of elements of a specific type. Here is the basic way to initialize an array during its declaration:
```cpp int list[5] = {0, 1, 2, 3, 4}; ``` This statement initializes an integer array `list` of size 5 with values from 0 to 4.
In our exercise, `list1` and `list2` are declared without explicit initialization. Instead, they are filled using a loop. This method allows for more dynamic or computed values, as the exercise demonstrates by setting values using calculations within the loop. Remember, uninitialized array elements can contain garbage values, so it’s essential to set them before utilizing.

output formatting

Understanding output formatting in C++ is key to displaying information in an organized and readable manner. The `cout` stream is used to output text and variables to the console.

In our example, we use the `cout` stream for displaying the contents of arrays `list1` and `list2`. Here's a breakdown of how output formatting is managed:

• The insertion operator `<<` is used to send data to the stream.
• Strings like `"list1: "` are printed before iterating over array elements, which gives context to the data being displayed.
• Each element of the array is followed by a space to neatly separate items in the output. After the loop, `endl` is used to ensure the cursor moves to the next line.

Proper formatting helps in troubleshooting and interpreting results, as it structures the output into a human-readable form. For more sophisticated formatting, one might opt to use additional libraries or features like `iomanip` for controlling width, precision, and alignment settings.