Welcome to our programming practice lesson! Are you ready for a challenging yet exciting task involving nested loops and arrays? We will unravel the skill of using nested loops to search through two arrays. Brace yourself for a remarkable journey of practical learning. Let's get started!

Your task is to create a function that takes two arrays of integers as input and returns pairs of integers. Each pair should consist of:

1. The first integer from the first array.
2. The second integer from the second array. However, there's a condition: the first integer in the pair must be less than the second integer. The output should be a list of strings, where each string represents a valid pair in the format "first second". The order of the pairs in the output must respect the order of the integers in the input arrays. For example: Given the arrays [1, 3, 7] and [2, 8, 9], the function should return: ["1 2", "1 8", "1 9", "3 8", "3 9", "7 8", "7 9"].

Keep in mind: If no valid pairs exist, the function should return an empty list. If either of the input arrays is empty, the result should also be an empty list.

Let's delve into this task step by step to uncover the solution!

Before venturing into the code, let's decode the problem. Nested looping fits perfectly here.

Start by creating an empty array named result to store our pairs.

TypeScript
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1function retrievePairs(array1: number[], array2: number[]): string[] {
2    let result: string[] = [];

Creating your function and data structure first is a wise strategy!

Now, the focus turns to forming the nested loops. You need to iterate over both arrays, and for this, you'll need nested loops. An outer loop will select one element from the first array, and an inner loop will scan through each element of the second array.

TypeScript
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1function retrievePairs(array1: number[], array2: number[]): string[] {
2    let result: string[] = [];
3    // Start of the outer loop: iterating through elements of array1
4    for (let i of array1) {
5        // Start of the inner loop: iterating through elements
6        // of array2 for each element of array1
7        for (let j of array2) {
8            // Our logic goes here
9        }
10    }
11    return result;
12}

In this setup, every element in array1 is represented by i, and for each i, j represents an element in array2.

With our loops ready, it's time to incorporate the logic. We run a check at this point: is the element i from array1 less than the element j from array2? If it's true, we insert the concatenated string ${i} ${j} into our result array.

TypeScript
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1function retrievePairs(array1: number[], array2: number[]): string[] {
2    let result: string[] = [];
3    
4    for (let i of array1) {
5        for (let j of array2) {
6            // Check if the element from array1 is less than the element from array2
7            if (i < j) {
8                // Add the valid pair to the result array
9                result.push(`${i} ${j}`);
10            }
11        }
12    }
13    // Return the final array of pairs
14    return result;
15}

During each execution of our inner loop, we perform this check and store the pairs that comply with our condition.

Now, let's see our function in action. We will use two sample arrays and invoke the retrievePairs function. The function will generate and return pairs of numbers meeting our criteria. Here's how you can use our function:

TypeScript
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1// Example usage
2let array1: number[] = [1, 3, 7];
3let array2: number[] = [2, 8, 9];
4let res: string[] = retrievePairs(array1, array2);
5    
6// Print each pair from the result array
7for (let pair of res) {
8    console.log(pair);
9}
10// Outputs "1 2", "1 8", "1 9", "3 8", "3 9", "7 8", "7 9"

In this example, we have two arrays [1, 3, 7] and [2, 8, 9]. The retrievePairs function processes these arrays to generate valid pairs. The results are printed to the console, showing how the function meets the task requirements effectively. You can experiment with other arrays to explore its operation further.

Fantastic job! You have successfully performed a complex task using nested loops to search through two arrays using TypeScript. You now possess the ability to traverse and manipulate two arrays effectively for a given purpose. Keep practicing and continue challenging yourself with more tasks to solidify your understanding. In your upcoming practice sessions, you will come across similar tasks that will further sharpen your programming skills. Remember, practice is the key to mastering any concept. Happy coding!