Step by Step solution about How to resolve the algorithm Range extraction step by step in the C++ programming language

The provided C++ code defines a function to extract and print ranges of consecutive numbers from an input sequence.

Here's a detailed explanation:

1. extract_ranges() Function:

   • Input Parameters:
     • begin: An input iterator pointing to the start of the sequence.
     • end: An input iterator pointing to the end of the sequence.
     • os: An output stream (e.g., std::cout) to which the extracted ranges will be printed.
   • Purpose: To extract and print consecutive number ranges from the input sequence.

2. Main Function:

   • It defines an integer array data[] containing a sequence of numbers.

   • It calls the extract_ranges() function with the address of the data array as the begin iterator, a pointer to the end of the array as the end iterator, and std::cout as the output stream.

3. end() Function (Helper Function):

   • This function is used internally by extract_ranges(). It takes an array array and its size n and returns a pointer to the element after the last element in the array (array + n).

4. Implementation of extract_ranges():

   • It initializes the current number (current) to the value at the beginning of the sequence (*begin) and prints it.
   • It initializes a count variable (count) to 1, indicating that a single number has been encountered so far.
   • It enters a loop that continues until the end of the sequence (begin != end).
   • Inside the loop, it checks the next number (next) in the sequence.
   • If next is one greater than the current number, it increments the count.
   • If next is not one greater than the current number, it prints the current range as follows:
     • If count is greater than 2, it prints a hyphen (-) to indicate a range of numbers.
     • If count is 2 or less, it prints a comma ( ,`) to separate numbers.
     • It prints the current number and the next number, separated by a comma if count is greater than 1.
     • It resets the count to 1.
   • After processing all numbers in the sequence, it checks the final count and prints the last range accordingly.

5. Output:

   • The provided input sequence data will produce the following output:

     0,1,2,4-8,11-12,14-25,27-33,35-39
     

#include <iostream>
#include <iterator>
#include <cstddef>

template<typename InIter>
 void extract_ranges(InIter begin, InIter end, std::ostream& os)
{
  if (begin == end)
    return;

  int current = *begin++;
  os << current;
  int count = 1;

  while (begin != end)
  {
    int next = *begin++;
    if (next == current+1)
      ++count;
    else
    {
      if (count > 2)
        os << '-';
      else
        os << ',';
      if (count > 1)
        os << current << ',';
      os << next;
      count = 1;
    }
    current = next;
  }

  if (count > 1)
    os << (count > 2? '-' : ',') << current;
}

template<typename T, std::size_t n>
 T* end(T (&array)[n])
{
  return array+n;
}

int main()
{
  int data[] = { 0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
                 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
                 25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
                 37, 38, 39 };

  extract_ranges(data, end(data), std::cout);
  std::cout << std::endl;
}