Step by Step solution about How to resolve the algorithm Ascending primes step by step in the Ruby programming language

The provided Ruby code snippet generates a list of prime numbers by combining digits from a given set in all possible ways and checking if the resulting number is prime. Here's a detailed explanation:

1. The code starts by requiring the 'prime' library, which provides methods for checking if a number is prime.

2. An array called digits is defined with the digits [9, 8, 7, 6, 5, 4, 3, 2, 1]. These digits represent the potential building blocks for creating prime numbers.

3. The code uses the flat_map method to generate a flattened list of prime numbers from the given digits. It does this by looping through each possible combination of digits, creating a number from the combination, and checking if that number is prime.

4. The 1.upto(digits.size) range generates numbers from 1 to the size of the digits array (9). This loop will generate combinations of 1, 2, 3, ..., up to 9 digits.

5. For each combination size n, the digits.combination(n) method generates all possible combinations of n digits from the digits array. For example, if n is 2, this will generate combinations like [9, 8], [9, 7], [8, 7], and so on.

6. The filter_map method is used to filter out non-prime numbers from the generated combinations. It checks if the join.to_i of the combination (which converts the combination of digits into an integer) is a prime number using the prime? method from the 'prime' library.

7. The resulting list of prime numbers is reversed using the reverse method. This step might be unnecessary depending on the desired output format.

8. Finally, the code converts the final list of prime numbers to a comma-separated string using the join(",") method and prints it to the console.

The output of the code will be a comma-separated list of prime numbers that can be formed by combining the digits from the digits array. The specific prime numbers generated will vary depending on the digits provided.

require 'prime'

digits = [9,8,7,6,5,4,3,2,1]
res = 1.upto(digits.size).flat_map do |n|
   digits.combination(n).filter_map do |set|
      candidate = set.join.to_i
      candidate if candidate.prime?
   end.reverse
 end

 puts res.join(",")