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LeetCode #21: Merge Two Sorted Lists

0 likes • Oct 15, 2022
Java
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merge sort

AustinLeath
0 likes • Nov 18, 2022
Java
import static java.lang.System.*;
import java.util.Arrays;
public class MergeSort{
private static int passCount;
public static void mergeSort(int[] list)
{
passCount=0;
mergeSort(list, 0, list.length);
}
private static void mergeSort(int[] list, int front, int back) //O( Log N )
{
int mid = (front+back)/2;
if(mid==front) return;
mergeSort(list, front, mid);
mergeSort(list, mid, back);
merge(list, front, back);
}
private static void merge(int[] list, int front, int back) //O(N)
{
int dif = back-front;
int[] temp = new int[dif];
int beg = front, mid = (front+back)/2;
int saveMid = mid;
int spot = 0;
while(beg < saveMid && mid < back) {
if(list[beg] < list[mid]) {
temp[spot++] = list[beg++];
} else {
temp[spot++] = list[mid++];
}
}
while(beg < saveMid)
temp[spot++] = list[beg++];
while(mid < back)
temp[spot++] = list[mid++];
for(int i = 0; i < back-front; i++) {
list[front+i] = temp[i];
}
System.out.println("pass " + passCount++ + " " + Arrays.toString(list) + "\n");
}
public static void main(String args[])
{
mergeSort(new Comparable[]{ 9, 5, 3, 2 });
System.out.println("\n");
mergeSort(new Comparable[]{ 19, 52, 3, 2, 7, 21 });
System.out.println("\n");
mergeSort(new Comparable[]{ 68, 66, 11, 2, 42, 31});
System.out.println("\n");
}
}
public static void enu2ecefCov(GMatrix ecefCov, GMatrix enuCov, LLA refLLA) {
double lambda = refLLA.longitude;
double phi = refLLA.latitude;
GMatrix R = new GMatrix(6, 6);
GMatrix Rt = new GMatrix(6, 6);
GMatrix tmp1 = new GMatrix(6, 6);
GMatrix tmp2 = new GMatrix(6, 6);
R.setElement(0, 0, -Math.sin(lambda));
R.setElement(0, 1, -Math.sin(phi)*Math.cos(lambda));
R.setElement(0, 2, Math.cos(phi)*Math.cos(lambda));
R.setElement(1, 0, Math.cos(lambda));
R.setElement(1, 1, -Math.sin(phi)*Math.sin(lambda));
R.setElement(1, 2, Math.cos(phi)*Math.sin(lambda));
R.setElement(2, 0, 0);
R.setElement(2, 1, Math.cos(phi));
R.setElement(2, 2, Math.sin(phi));
R.setElement(3, 3, -Math.sin(lambda));
R.setElement(3, 4, -Math.sin(phi)*Math.cos(lambda));
R.setElement(3, 5, Math.cos(phi)*Math.cos(lambda));
R.setElement(4, 3, Math.cos(lambda));
R.setElement(4, 4, -Math.sin(phi)*Math.sin(lambda));
R.setElement(4, 5, Math.cos(phi)*Math.sin(lambda));
R.setElement(5, 3, 0);
R.setElement(5, 4, Math.cos(phi));
R.setElement(5, 5, Math.sin(phi));
Rt.transpose(R);
tmp1.mul(enuCov, R);
ecefCov.mul(Rt, tmp1);
}

quick sort

CodeCatch
0 likes • Nov 19, 2022
Java
import java.util.Arrays;
public class QuickSortMain {
private static int array[];
public static void sort(int[] arr) {
if (arr == null || arr.length == 0) {
return;
}
array = arr;
quickSort(0, array.length-1);
}
private static void quickSort(int left, int right) {
int i = left;
int j = right;
// find pivot number, we will take it as mid
int pivot = array[left+(right-left)/2];
while (i <= j) {
/**
* In each iteration, we will increment left until we find element greater than pivot
* We will decrement right until we find element less than pivot
*/
while (array[i] < pivot) { i++; } while (array[j] > pivot) {
j--;
}
if (i <= j) {
exchange(i, j);
//move index to next position on both sides
i++;
j--;
}
}
// call quickSort() method recursively
if (left < j)
quickSort(left, j);
if (i < right)
quickSort(i, right);
}
private static void exchange(int i, int j) {
int temp = array[i];
array[i] = array[j];
array[j] = temp;
}
public static void main(String a[]){
int[] input = {33,21,45,64,55,34,11,8,3,5,1};
System.out.println("Before Sorting : ");
System.out.println(Arrays.toString(input));
sort(input);
System.out.println("==================");
System.out.println("After Sorting : ");
System.out.println(Arrays.toString(array));
}
}

try-catch modularity

AustinLeath
0 likes • Jan 31, 2023
Java
public class UserService {
private UserRepository userRepository;
public UserService(UserRepository userRepository) {
this.userRepository = userRepository;
}
public User getUserById(long id) {
try {
return userRepository.getUserById(id);
} catch (Exception e) {
// Log the exception here
System.out.println("An error occurred while fetching the user: " + e.getMessage());
return null;
}
}
}
public class UserRepository {
public User getUserById(long id) throws Exception {
// Database query to fetch the user
if (id < 0) {
throw new Exception("Invalid user id");
}
// Return the user object
return new User(id, "John Doe");
}
}
public class User {
private long id;
private String name;
public User(long id, String name) {
this.id = id;
this.name = name;
}
public long getId() {
return id;
}
public String getName() {
return name;
}
}

Send Email from Java

CodeCatch
0 likes • Nov 19, 2022
Java
import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;
public void postMail( String recipients[ ], String subject, String message , String from) throws MessagingException
{
boolean debug = false;
//Set the host smtp address
Properties props = new Properties();
props.put("mail.smtp.host", "smtp.example.com");
// create some properties and get the default Session
Session session = Session.getDefaultInstance(props, null);
session.setDebug(debug);
// create a message
Message msg = new MimeMessage(session);
// set the from and to address
InternetAddress addressFrom = new InternetAddress(from);
msg.setFrom(addressFrom);
InternetAddress[] addressTo = new InternetAddress[recipients.length];
for (int i = 0; i < recipients.length; i++)
{
addressTo[i] = new InternetAddress(recipients[i]);
}
msg.setRecipients(Message.RecipientType.TO, addressTo);
// Optional : You can also set your custom headers in the Email if you Want
msg.addHeader("MyHeaderName", "myHeaderValue");
// Setting the Subject and Content Type
msg.setSubject(subject);
msg.setContent(message, "text/plain");
Transport.send(msg);
}

Random Integers -> file

CodeCatch
0 likes • Nov 19, 2022
Java
//sample code to write 100 random ints to a file, 1 per line
import java.io.PrintStream;
import java.io.IOException;
import java.io.File;
import java.util.Random;
public class WriteToFile {
public static void main(String[] args) {
try {
PrintStream writer = new PrintStream(new File("randInts.txt"));
Random r = new Random();
final int LIMIT = 100;
for (int i = 0; i < LIMIT; i++) {
writer.println(r.nextInt());
}
writer.close();
} catch (IOException e) {
System.out.println("An error occured while trying to write to the file");
}
}
}