Arrays to the finish

Finding pairs

Constructed from memory... I hope it resembles what we did...

Reversing an array...

(Thank you for sending me these!!)

In place

	public class reversereverse {
	public static void main(String[] args){
	int[] data = {1, 2, 3, 4, 5, 6, 7, 8, 9};
	for (int i = 0; i<data.length/2; i++){
	int a = data[i];
	data[i] = data[data.length - i - 1];
	data[data.length - i - 1] = a;
	}
	System.out.println(java.util.Arrays.toString(data));
	}
	}

view raw reversereverse.java hosted with ❤ by GitHub

As a copy

	public class reverseagain {
	public static void main(String[] args){
	int[] data = {1, 2, 3, 4, 5};
	System.out.println(java.util.Arrays.toString(data));
	int[] newData = new int[data.length];
	System.out.println(java.util.Arrays.toString(newData));
	for(int i=0; i<data.length; i++){
	newData[i] = data[data.length - i -1];
	System.out.println(java.util.Arrays.toString(newData));
	}
	System.out.println(java.util.Arrays.toString(newData));
	}
	}

view raw reverseagain.java hosted with ❤ by GitHub

Some cellular automaton thing

That we didn't really finish... so don't worry about what it means :)

	public class Cells {
	public static void main(String[] args) {
	int[] data = { 0, 1, 1, 0, 1, 0 };
	System.out.println(java.util.Arrays.toString(data));
	int[] data2 = new int[data.length];
	for (int i=0; i<data.length; i++) {
	if (data[i] == 1) {
	data2[i] = 0;
	}
	else {
	data2[i] = 1;
	}
	}
	System.out.println(java.util.Arrays.toString(data2));
	}
	}

view raw Cells.java hosted with ❤ by GitHub

See you Tuesday!

Code from 10/18

Palindrome

	public class Pal {
	public static void main(String[] args) {
	String word = "Racecar";
	word = word.toLowerCase();
	boolean ok = true;
	for (int n=0; n<=word.length()-1; n++) {
	if (word.charAt(n) == word.charAt(word.length() - n - 1)) {
	}
	else {
	ok = false;
	break;
	}
	}
	if (ok) {
	System.out.println("Yes");
	}
	else {
	System.out.println("No");
	}
	}
	}

view raw Pal.java hosted with ❤ by GitHub

Anagrams...

So we didn't finish this one in recitation and on reflection it's really way too long... Here's a solution someone emailed me (sorry I forgot to ask you if you were OK with me sharing this if you mind I'll take it down) (also I reformatted a little)

	public class Anagram {
	public static void main(String[] args) {
	String a = IO.readString();
	String b = IO.readString();
	boolean anagram = true;
	int count = 0;
	if (a.length()==b.length()) {
	for ( int i = 0 ; i < a.length() ; i++) {
	char x = a.charAt(i);
	for ( int j = 0 ; j < b.length() ; j++ ) {
	if (x==b.charAt(j)) {
	count++;
	}
	if (x==a.charAt(j)) {
	count--;
	}
	}
	if (count!=0) {
	anagram = false;
	}
	}
	} else {
	anagram = false;
	}
	System.out.println(anagram);
	}
	}

view raw Anagram.java hosted with ❤ by GitHub

See you Tuesday!

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!