Arrays

[katherinejonesin]

Write your question here.
I don't understand this code

  string *const p = new string[n]; 
  string s;
   string *q = p;                   
     while (cin >> s && q != p + n)
    *q++ = s;                    
const size_t size = q - p;       
delete[] p;  

[lastchance]

It does roughly the same as this. Nothing useful because the array is deleted as soon as you have filled it.

   vector<string> p( n );
   for ( int i = 0; i < n; i++ )
   {
      cin >> p[i];
   }
   int size = n;

string *const p = new string[n];        // create a new array of size n
  string s;                             // declare a string variable
   string *q = p;                       // point q at the start of the array                    
     while (cin >> s && q != p + n)     // input strings (into s) until q points beyond the end of the array
    *q++ = s;                           // set the array element pointed to by q to string s, then advance q to point at the next element 
const size_t size = q - p;              // this simply sets the size of the array; size = n would do       
delete[] p;                             // delete the array you have input ... and done nothing with!   

[Enoizat]

Once understood, shortened code is probably the easiest to read, but sometimes we need to follow the logic step by step.

Perhaps this version is a bit clearer:

#include <iostream>
#include <string>


int main()
{
    constexpr std::size_t init_size { 4 };

    // Reserve space for init_size std::strings: 
    std::string* const p = new std::string[init_size];

    // Declare a new pointer to be modified - we don't want to modify 'p'!!
    std::string* q = p;

    std::cout << "Please insert " << init_size + 1
              << " words separated by space and press ENTER: ";

    for ( std::string s; std::cin >> s && q != p + init_size; ++q ) {
        *q = s;
    }

    const std::size_t guessed_size = q - p;

    delete[] p;

    std::cout << "initial size: " << init_size
              << "; guessed size: " << guessed_size
              << '\n';
}

[lastchance]

Actually the original code isn't very good, because it will require you to input n+1 things before storing the first n in an array.

The order of the two 'AND'ed things in the while condition should be reversed.
while ( q != p + n && cin >> s )

[dutch]

The original code is meaningless. Look at the OPs next post. Obviously an ad.