Hello, I was going through a beginner's guide book on C++ and could not understand exactly how this example works, even after pondering for hours.

This program is a card-dealing program which uses a 52-element array in which each element corresponds to a card. Once a card is picked, this array is updated to show that the card should be skipped in the future.

I mainly have problems with the select_next_available card function.Code:#include <iostream> #include <stdlib.h> #include <time.h> #include <math.h> using namespace std; int rand_0toN1(int n); void draw_a_card(); int select_next_available(int n); char *suits[4] = {"hearts", "diamonds", "spades", "clubs"}; char *ranks[13] = {"ace", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "jack", "queen", "king" }; int card_drawn[52]; int cards_remaining = 52; int main() { int n, i; srand(time(NULL)); // Set seed for random numbers. while (1) { cout << "Enter no. of cards to draw (0 to exit): "; cin >> n; if (n == 0) break; for (i = 1; i <= n; i++) draw_a_card(); } return 0; } // Draw-a-card function // Performs one card-draw by getting a random 0-4 and a random // 0-12. These are then used to index the string arrays, ranks // and suits. // void draw_a_card() { int r; // Random index (0 thru 12) into ranks array int s; // Random index (0 thru 3) into suits array int n, card; n = rand_0toN1(cards_remaining--); card = select_next_available(n); r = card % 13; // r = random 0 to 12 s = card / 13; // s = random 0 to 3 cout << ranks[r] << " of " << suits[s] << endl; } // Select-next-available-card function. // Find the Nth element of card_drawn, skipping over all those // elements already set to true. // int select_next_available(int n) { int i = 0; // At beginning of deck, skip past cards already drawn.while (card_drawn[i])i++; while (n-- > 0) { // Do the following n times: i++; // Advance to next card while (card_drawn[i]) // Skip past cards i++; // already drawn. } card_drawn[i] = true; // Note card to be drawn return i; // Return this number. } // Random 0-to-N1 Function. // Generate a random integer from 0 to N-1. // int rand_0toN1(int n) { return rand() % n; }

1.for the " while (card_drawn[i]) ", how is the condition card_drawn[i] used? The initial value of i is 0, so card_drawn[0] is false and the loop shouldnt even start in the first place?

2.For the while (n-- > 0) loop, does that mean n is further reduced by one here? What is the purpose of doing n--, and if n is initially zero (the rand_0toN1 function picks 0 from the numbers 0 to 51), then n-- = -1??

3.Lastly, why is i increased so many times in this function? I can see i++ three times here.

This example is really getting on my nerves~

Thanks!