Welcome! In today's lesson, we will explore the concept of slices in Go, specifically focusing on pairing up 'opposite' elements. We will learn how to access and manipulate elements within a Go slice. This task is a fantastic way to enhance your skills in handling slices within the Go programming language. Are you ready to begin? Let's dive in!

Our task today is to form pairs of 'opposite' elements in a given slice of integers. In a slice consisting of n elements, the first and last elements are considered 'opposite,' the second element and the second last element are 'opposite,' and so forth. For a slice with an odd number of elements, the middle element is its own 'opposite.'

You will be provided with a slice of n integers. The value of n can range from 1 to 100, inclusive. Your task is to return a new slice containing tuples (pairs) of elements and their 'opposite' elements.

Let's use an example slice numbers := []int{1, 2, 3, 4, 5} to better understand. In this case, the output of our solution(numbers) function will be []tuple{{1, 5}, {2, 4}, {3, 3}, {4, 2}, {5, 1}}.

Before we proceed to pair elements, let’s take a moment to quickly introduce structs in Go, which we'll use to organize our pairs.

A struct in Go is a composite data type that allows grouping together variables, called fields, of different types under a single name. The syntax to define a struct begins with the type keyword, followed by the name of the struct, the struct keyword, and the fields inside curly braces. For example:

Go
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1type tuple struct {
2    first  int
3    second int
4}

In this case, tuple is a struct with two fields, first and second, both of type int. This struct will serve as our container for storing pairs of 'opposite' elements.

Now, let's get back to the task at hand and let's figure out how to access an element's 'opposite.'

The 'opposite' of the i-th element of the slice is the element at the len(numbers) - i - 1-th position. To illustrate this, imagine standing at the start of a line and your friend standing at the end of the line. In this scenario, you and your friend could be considered 'opposites.' Similarly, the 'opposite' of numbers[0] is numbers[len(numbers) - 0 - 1], the 'opposite' of numbers[1] is numbers[len(numbers) - 1 - 1], and so on.

Now that we grasp how to locate an element's 'opposite,' we can proceed to code our solution. Let's start by initializing an empty slice of pairs to store our 'opposite' pairs and determine the slice's length for future reference.

Go
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1type tuple struct {
2    first  int
3    second int
4}
5
6func solution(numbers []int) []tuple {
7    result := []tuple{}
8    n := len(numbers)

The next step is to loop through all elements in our numbers slice. Within our loop, we'll create a tuple for each pairing of 'opposite' elements. This tuple will consist of the i-th element and the n - i - 1-th element. We will then append this tuple to our result slice. Here's the completed version of our function:

Go
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1type tuple struct {
2    first  int
3    second int
4}
5
6func solution(numbers []int) []tuple {
7    result := []tuple{}
8    n := len(numbers)
9    for i := 0; i < n; i++ {
10        result = append(result, tuple{numbers[i], numbers[n - i - 1]})
11    }
12    return result
13}

This function iterates over all the elements of the slice. For each of these elements, it forms a tuple with its 'opposite' and subsequently appends the pair to the result slice.

Great job! You've successfully navigated through the concept of 'opposite' pairs and slice indexing in Go. By now, you should be familiar with the notion of accessing and pairing elements in a slice based on their positions. This fundamental step is essential in mastering slice manipulation within Go. Up next, we've prepared a series of hands-on exercises for you to apply and further practice what you've learned today. Remember, practice makes perfect. Keep up the great work, and happy coding!