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!