Code from our exam review

Hi Everyone! Here's code we worked on on Tuesday (10/11). Here's the Nth Prime puzzle:

	public class Primes {
	public static void main(String[] args) {
	int n = 34;
	int count = 0;
	// for (int k=2; ; k++) {
	int k = 2;
	while (true) {
	boolean isPrime = true;
	// for (int j=2; j<k; j++) {
	int j = 2;
	while (j < k) {
	if (k % j != 0) {
	}
	else {
	isPrime = false;
	break;
	}
	j++;
	}
	if (isPrime) {
	count++;
	}
	if (count == n) {
	System.out.println(k);
	return;
	}
	k++;
	}
	}
	}

view raw Primes.java hosted with ❤ by GitHub

Here's the 7s puzzle:

	public class Sevens {
	public static void main(String[] args) {
	int min = 1;
	int max = 100;
	int seven = 0;
	for (int k=min; k<=max; k++) {
	if ((k / 1) % 10 == 7) {
	seven++;
	}
	if ((k / 10) % 10 == 7) {
	seven++;
	}
	if ((k / 100) % 10 == 7) {
	seven++;
	}
	if ((k / 1000) % 10 == 7) {
	seven++;
	}
	if ((k / 10000) % 10 == 7) {
	seven++;
	}
	}
	System.out.println(seven);
	}
	}

view raw Sevens.java hosted with ❤ by GitHub

Here's the highest-lowest puzzle:

	public class SmLr {
	public static void main(String[] args) {
	int stop = IO.readInt();
	int input = IO.readInt();
	int highest = input;
	int lowest = input;
	while (input != stop) {
	if (input > highest) {
	highest = input;
	}
	if (input < lowest) {
	lowest = input;
	}
	input = IO.readInt();
	}
	System.out.println(lowest);
	System.out.println(highest);
	}
	}

view raw SmLr.java hosted with ❤ by GitHub

You're probably forgotten all about this by now, but here's that timing puzzle we did the week before. It doesn't quite work yet... but it's sooo close:

	public class Time {
	public static void main(String[] args) {
	long now = System.currentTimeMillis();
	int count = 0;
	while (System.currentTimeMillis() - now <= 100) {
	Math.sin(2);
	count++;
	}
	long after = System.currentTimeMillis();
	long diff = after - now;
	System.out.println(diff / count);
	}
	}

view raw Time.java hosted with ❤ by GitHub

And then there's that 3n+1 puzzle:

	public class Collatz {
	public static void main(String[] args) {
	int n;
	int count = 0;
	int highest = 0;
	int k = 1;
	for ( int i = 1; i<=100 ; i++) {
	n = i;
	count = 0;
	while (n != 1) {
	if (n % 2 == 0) {
	n = n / 2;
	//System.out.println(n);
	}
	else {
	n = n * 3 +1;
	//System.out.println(n);
	}
	count++;
	}
	if (count > highest) {
	highest = count;
	k = i;
	}
	//System.out.println(count);
	}
	System.out.println(k);
	System.out.println(highest);
	}
	}

view raw Collatz.java hosted with ❤ by GitHub

Everyone, good luck on the exam!! I hope it goes wonderfully. If you have any questions or concerns or opinions or rants or hopes or dreams you can email me. Or if there's some code I forgot to put up here that you'd like to see. See you next week!