// CSE 142, Winter 2008, Marty Stepp
//
// This program computes and prints prime numbers.
// This is an example of a fencepost problem.

public class Primes {
	public static void main(String[] args) {
		printPrimes(1);
		printPrimes(2);
		printPrimes(50);
		printPrimes(53);
		printPrimes(1000);

		printPrimes2(50, 100);
	}
	
	// Prints all prime numbers up to the given maximum.
	public static void printPrimes(int max) {
		System.out.print("[");
		if (max > 1) {
			System.out.print(2);
			// for each number up to max,
			//    if that number is prime,
			//        print that number
			for (int i = 3; i <= max; i++) {
				if (countFactors(i) == 2) {
					// i is prime
					System.out.print(", " + i);
				}
			}
		}
		System.out.println("]");
	}

	// Prints all prime numbers between the given minimum and maximum values.
	public static void printPrimes2(int min, int max) {
		System.out.print("[");
		int count = 0;
		if (max > 1) {
			// for each number up to max,
			//    if that number is prime,
			//        print that number
			for (int i = min; i <= max; i++) {
				if (countFactors(i) == 2) {
					// i is prime
					count++;
					if (count > 1) {
						System.out.print(", ");
					}
					System.out.print(i);
				}
			}
		}
		System.out.println("]");
	}

	// Returns the number of factors of the given integer.
	// Assumes that a non-negative number is passed.
	// (This code comes from a previous lecture.)
	public static int countFactors(int number) {
		int count = 0;
		for (int i = 1; i <= number; i++) {
			if (number % i == 0) {
				// i is a factor of the number
				count++;
			}
		}

		return count;
	}
}