Assign values to array that have multible variables in java

Assign values to array that have multible variables in java - java

I had created an array of the following class , when I try to assign new values it gives me null
my code as follows
public class edge {
public double w = 0 ;
public int a = 0 ;
public int b = 0 ;
}
edge edges[];
edges = new edge[5];
int c = 10
for ( int i = 0 , i< 5 , i++) {
edges[i]=new edge();
edges[i].a = i;
edges[i].b = i + 1;
edges[i].w = i/c ;
}

You have some problems in your code :
First : you should not put your code outside your class like you do
Secondd: you have to use the main method to start your program
Third : you should to separate your statement in your loop with ; and not with , your program should look like this :
public class Edge {
public double w = 0;
public int a = 0;
public int b = 0;
public static void main(String[] args) {
Edge edges[];
edges = new Edge[5];
int c = 10;
for (int i = 0; i < 5; i++) {
edges[i] = new Edge();
edges[i].a = i;
edges[i].b = i + 1;
edges[i].w = i / c;
}
}
}
Or you can separate them in differentiate classes like this :
public class Cls {
public static void main(String[] args) {
Edge edges[];
edges = new Edge[5];
int c = 10;
for (int i = 0; i < 5; i++) {
edges[i] = new Edge();
edges[i].a = i;
edges[i].b = i + 1;
edges[i].w = i / c;
}
System.out.println(Arrays.toString(edges));
//Output
//[edge{w=0.0, a=0, b=1}, edge{w=0.0, a=1, b=2}, edge{w=0.0, a=2, b=3}, edge{w=0.0, a=3, b=4}, edge{w=0.0, a=4, b=5}]
}
}
class Edge {
public double w = 0;
public int a = 0;
public int b = 0;
#Override
public String toString() {
return "edge{" + "w=" + w + ", a=" + a + ", b=" + b + '}';
}
}

Related

How to correctly implement maximum weight independent set of positive tree using BFS

can someone help me implement the maximum weight independent set for a TREE (not a graph)?
The tree is represented by an adjacency matrix, and we have an array for the weights of the vertices.
BFS output: // 0: distances from start vertex
// 1: BFS-order
// 2: parent-IDs
I tried this code, it doesn't work on all test cases and it says most of the time that the weight is too small.
Can someone help me find the errors?
import java.io.*;
import java.util.*;
public class Lab5
{
/**
* Problem: Find a maximum weight independent set using dynammic programming.
*/
private static int[] problem(Tree t, int[] weights)
{
// Implement me!
//base cases
if (t.noOfVertices==0) {
return new int[] {};
}
if (t.noOfVertices==1) {
return new int[] {weights[0]};
}
//we will implement this using bfs, we will use 0 as the root
int[][] bfs = t.bfs(0);
//finding leaves
int leaf[] = new int [t.noOfVertices];
//now we can implement our algorithm
//M is the maximum weight of the tree if it contains i, and M1 is the maximum weight of the tree if it doesn't contain i
int M[]=new int[t.noOfVertices];
int M1[]=new int[t.noOfVertices];
//treating elements that aren't leaves
int nodeDiscovered[] = new int[t.noOfVertices];
for (int i = 0; i<t.noOfVertices; i++) {
if (t.edges[i].length==1) {
leaf[i]=1;
M[i]=weights[i];
nodeDiscovered[i]=1;
M1[i]=0;
}
else {
leaf[i]=0;
nodeDiscovered[i]=0;
}
}
for (int i = 1; i<t.noOfVertices; i++) {
if (leaf[i]==1) {
int node = bfs[2][i];
if (nodeDiscovered[node]!=0) {
continue;
}
while (node>-1) {
int parent = bfs[2][node];
ArrayList<Integer> sibs = new ArrayList<Integer>();
if (parent!=-1) {
for (int j = 0; j<t.edges[parent].length; j++) {
if (t.edges[parent][j]!=bfs[2][parent]) {
sibs.add(t.edges[parent][j]);
}
}
}
else {
sibs.add(node);
}
for (int sib : sibs) {
if (nodeDiscovered[sib]!=0) {
continue;
}
M[sib]=weights[sib];
for (int k : t.edges[sib]) {
if(bfs[0][sib]==bfs[0][k]-1) {
M[sib]=M[sib]+M1[k];
M1[sib]+=(M[k]>M1[k])?M[k]:M1[k];
}
}
nodeDiscovered[sib]=1;
}
node = bfs[2][node];
}
}
}
//putting the answers in an arraylist
ArrayList<Integer> set = new ArrayList<Integer>();
if (M[0]>M1[0]) {
set.add(0);
}
for (int i = 1; i<t.noOfVertices; i++) {
if (!set.contains(bfs[2][i]) && M[i]>=M1[i] ) {
set.add(i);
}
}
System.out.println(set);
//putting the elements of the arraylist into an array of int
int[] set1 = new int[set.size()];
for (int i = 0; i<set.size(); i++) {
set1[i]=set.get(i);
}
return set1;
}
// ---------------------------------------------------------------------
// Do not change any of the code below!
// Do not change any of the code below!
/**
* Determines if a given set of vertices is an independent set for the given tree.
*/
private static boolean isIndSet(Tree t, int[] set)
{
if (set == null) return false;
boolean[] covered = new boolean[t.noOfVertices];
for (int i = 0; i < set.length; i++)
{
int vId = set[i];
int[] neighs = t.edges[vId];
if (covered[vId]) return false;
covered[vId] = true;
for (int j = 0; j < neighs.length; j++)
{
int nId = neighs[j];
covered[nId] = true;
}
}
return true;
}
private static final int LabNo = 5;
private static final String course = "CS 427";
private static final String quarter = "Fall 2021";
private static final Random rng = new Random(190817);
private static boolean testProblem(int[][] testCase)
{
int[] parents = testCase[0];
int[] weights = testCase[1];
Tree t = Tree.fromParents(parents);
int[] solution = maxIsWeight(t, weights);
int isWeight = solution[0];
int isSize = solution[1];
int[] answer = problem(t, weights.clone());
if (!isIndSet(t, answer))
{
System.out.println("Not an independent set.");
return false;
}
int ansWeight = 0;
for (int i = 0; i < answer.length; i++)
{
ansWeight += weights[answer[i]];
}
if (ansWeight < isWeight)
{
System.out.println("Weight too small.");
return false;
}
if (answer.length < isSize)
{
System.out.println("Set too small.");
return false;
}
return true;
}
private static int[] maxIsWeight(Tree t, int[] weigh)
{
int n = t.noOfVertices;
int[][] dfs = t.dfs(0);
int[] post = dfs[2];
int[] w = new int[n];
for (int i = 0; i < n; i++)
{
w[i] = weigh[i] * n + 1;
}
boolean[] isCandidate = new boolean[n];
for (int i = 0; i < n; i++)
{
int vId = post[i];
if (w[vId] <= 0) continue;
isCandidate[vId] = true;
int[] neighs = t.edges[vId];
for (int j = 0; j < neighs.length; j++)
{
int uId = neighs[j];
w[uId] = Math.max(w[uId] - w[vId], 0);
}
}
int isWeight = 0;
int isSize = 0;
for (int i = n - 1; i >= 0; i--)
{
int vId = post[i];
if (!isCandidate[vId]) continue;
isWeight += weigh[vId];
isSize++;
int[] neighs = t.edges[vId];
for (int j = 0; j < neighs.length; j++)
{
int uId = neighs[j];
isCandidate[uId] = false;
}
}
return new int[] { isWeight, isSize };
}
public static void main(String args[])
{
System.out.println(course + " -- " + quarter + " -- Lab " + LabNo);
int noOfTests = 300;
boolean passedAll = true;
System.out.println("-- -- -- -- --");
System.out.println(noOfTests + " random test cases.");
for (int i = 1; i <= noOfTests; i++)
{
boolean passed = false;
boolean exce = false;
try
{
int[][] testCase = createProblem(i);
passed = testProblem(testCase);
}
catch (Exception ex)
{
passed = false;
exce = true;
ex.printStackTrace();
}
if (!passed)
{
System.out.println("Test " + i + " failed!" + (exce ? " (Exception)" : ""));
passedAll = false;
//break;
}
}
if (passedAll)
{
System.out.println("All test passed.");
}
}
private static int[][] createProblem(int testNo)
{
int size = rng.nextInt(Math.min(testNo, 5000)) + 5;
// -- Generate tree. ---
int[] parents = new int[size];
parents[0] = -1;
for (int i = 1; i < parents.length; i++)
{
parents[i] = rng.nextInt(i);
}
// -- Generate weights. ---
int[] weights = new int[size];
for (int i = 0; i < weights.length; i++)
{
weights[i] = rng.nextInt(256);
}
return new int[][] { parents, weights };
}
}
I attached an image that contains the algorithm that I used.

How can I compile this program?

I have a problem with compilation of this program I don't know how can I solve this problem
class ArrayTester{
public void arrayTester(ArrayDeque arrayDeque) {
List evenlist = new ArrayList();
List oddlist = new ArrayList();
for (int n = 0; n < arrayDeque.size(); n++) {
if (arrayDeque.Length() % 2 == 0) {
arrayDeque.addAll(evenlist);
} else {
arrayDeque.addAll(oddlist);
}
System.out.println(evenlist);
System.out.println(oddlist);
}
}
}
class Kodilla {
public static void main(String[] args) {
ArrayDeque<String> arrayDeque = new ArrayDeque<>();
Random random = new Random();
String text = "";
int howLong = random.nextInt(50) + 1;
while (text.length() < howLong) {
text = text + "a";
for (int i = 0; i < 50; i++) {
arrayDeque.add(text);
System.out.println(arrayDeque);
System.out.println(arrayDeque.size());
arrayTester tester = new ArrayTester();
tester.arrayTester(arrayDeque);
System.out.println(arrayTester);
}
}
}
}

what I see is that in this line
arrayTester tester = new ArrayTester();
there is typo in the variable definition. (lowercase a)

How do I fill an ArrayList with random generated products?

I'd like some help with getting a randomizer working for my code. I am working on a hill-climbing algorithm for a school project. The algorithm works only I don't know how I can make it add random product(locations it needs to visit.)
Here is the main class. If I have to provide anymore then feel free to ask and I will.
package hillclimbing;
import java.util.ArrayList;
import java.util.Arrays;
public class Driver {
private ArrayList<Product> initialProducts = new ArrayList<Product>(Arrays.asList(
new Product("Tandpasta", 42.3601, -71.0589),
new Product("Banaan", 29.7064, -95.3698),
new Product("Kaas", 30.2672, -97.7431),
new Product("Laptop", 37.7749, -122.4194),
new Product("Vliegtuig", 39.0000, -104.0000),
new Product("Robot", 34.0000, -118.0000),
new Product("Magazijn", 41.0000, -87.0000),
new Product("Kubus", 40.0000, -74.0000),
new Product("Doos", 32.0000, -96.0000),
new Product("Lego", 47.0000, -122.0000)
));
public static void main(String[] args) {
Driver driver = new Driver();
Route route = new Route(driver.initialProducts);
printHeading(route);
System.out.print(route + " | " + route.getTotalDistance());
new HillClimbing().findShortestRoute(route);
}
public static void printHeading(Route route){
String headingColumn1 = "Route";
String remainingHeadingColumns = "Distance (in miles) | Compare adjacent to current route";
int productNamesLength = 0;
for(int x = 0; x < route.getProducts().size(); x++) productNamesLength += route.getProducts().get(x).getName().length();
int arrayLength = productNamesLength + route.getProducts().size()*2;
int partialLength = (arrayLength - headingColumn1.length()/2);
for(int x = 0; x < partialLength; x++)System.out.print(" ");
System.out.print(headingColumn1);
for(int x = 0; x < partialLength; x++)System.out.print(" ");
if((arrayLength % 2) == 0)System.out.print(" ");
System.out.println(" | " + remainingHeadingColumns);
productNamesLength += remainingHeadingColumns.length() + 3;
for(int x = 0; x < productNamesLength + route.getProducts().size()*2; x++)System.out.print("-");
System.out.println("");
}
}
And here is the randomizer that should be able to fill/replace the ArrayList
package hillclimbing;
import java.util.*;
public class RandomProducten {
public HashMap<Integer, Product> producten;
public RandomProducten(int aantal){
Random rand = new Random();
producten = new HashMap<Integer, Product>();
for(int i = 1; i <= aantal;i++){
boolean geaccepteerd = false;
int randx = rand.nextInt(5) + 1;
int randy = rand.nextInt(5) + 1;
while (! geaccepteerd){
if (hasDuplicates(randx, randy)){
randx = rand.nextInt(5) + 1;
randy = rand.nextInt(5) + 1;
} else {
geaccepteerd = true;
}
}
Product p = new Product("Product " + i, randx, randy);
producten.put(i, p);
}
}
public boolean hasDuplicates(int x, int y) {
boolean antwoord = false;
for (Map.Entry<Integer, Product> entry : producten.entrySet()) {
if (entry.getValue().getX() == x && entry.getValue().getY() == y){
antwoord = true;
}
}
return antwoord;
}
public String toString(){
String antwoord = "";
for (Map.Entry<Integer, Product> entry : producten.entrySet()) {
antwoord += entry.getValue();
}
return antwoord;
}
}

Create a Matrix from an ArrayList

I want to create a class that creates a Matrix via an ArrayList.
So that's what I did:
public class Matrice implements IMatrice {
ArrayList elements;
private int numLignes;
private int numColonnes;
public static void main(String[] args) {
Matrice test = new Matrice(3, 4, 6.0);
System.out.println(test);
}
public Matrice (int numLignes, int numColonnes, double valeur){
this.numLignes = numLignes;
this.numColonnes = numColonnes;
elements = new ArrayList(numLignes * numColonnes);
for(int i = 0; i < numLignes * numColonnes; i++){
elements.add(i, valeur);
}
}
}
Now that i created this, I wanted to try if it works. Then I created this toString() method:
public String toString() {
final DecimalFormat DEC_FORMAT = new DecimalFormat("0.0");
final int ESP = 8;
int num;
String sTmp;
String s = "[";
for (int i = 0 ; i < (numLignes * numColonnes) ; i++) {
//etendre i sur ESP colonnes
sTmp = "";
num = ESP - DEC_FORMAT.format(elements.get(i)).length();
for (int j = 0 ; j < num ; j++) {
sTmp = sTmp + " ";
}
sTmp = sTmp + DEC_FORMAT.format(elements.get(i));
if (i != 0 && i % numColonnes == 0) {
s = s + " ]\n[" + sTmp;
} else {
s = s + sTmp;
}
}
s = s + " ]";
return s;
}
Then this is my main to try the Matrix:
public static void main(String[] args) {
Matrice test = new Matrice(3, 4, 6.0);
System.out.println(test);
}
and i don't know why but i only get this :
[ ]
I know that a little thing is wrong but I can't find what. Could you help me?

Okay, i messed up...
The problem was in here :
elements.add(i, valeur);
i did a mistake... i mingled with the set() method.
here is the correction :
elements.add(valeur);

I am getting null values in my Array

I am playing around with an ArrayList and trying to get it to grow twice it's size every time it exceeds it's size. Here is my add method:
public class ArrayExpander
{
private int size;
private int noOfItems;
private Object[] store;
private final int INITIALSIZE = 2;
public ArrayExpander()
{
store = new Object[INITIALSIZE];
noOfItems = 0;
size = INITIALSIZE;
}
public void add(Object obj)
{
growBufferIfNecessary();
store[size++] = obj;
/*for (int i = size - 1; i < store.length; i++)
{
store[i] = store[i - 1];
store[i] = obj;
}*/
}
public String toString()
{
String temp = "[" + store[0];
for (int i = 1; i < size; i++)
{
temp = temp + "," + store[i];
}
temp = temp + "]";
return temp;
}
private void growBufferIfNecessary()
{
if (size == store.length)
{
Object[] newStore = new Object[2 * store.length];
for (int i = 0; i < store.length; i++)
{
newStore[i] = store[i];
}
store = newStore;
}
}
public static void main(String[] args)
{
ArrayExpander ae = new ArrayExpander();
//System.out.println(ae);
ae.add("a");
ae.add("b");
System.out.println(ae);
ae.add("c");
ae.add("d");
ae.add("e");
ae.add("f");
ae.add("g");
ae.add("h");
System.out.println(ae);
ae.add("i");
System.out.println(ae);
}
}
Here is my output:
[null,null]
[null,null,a,b]
[null,null,a,b,c,d,e,f,g,h]
[null,null,a,b,c,d,e,f,g,h,i]
I can't figure out why I am getting the null statements. The first line should be a,b and then the arraylist should double in size and be a,b,c,d. I have it set for final int INITIALSIZE = 2.
The output I am looking for is
[a,b]
[a,b,c,d]
[a,b,c,d,e,f,g,h]
[a,b,c,d,e,f,g,h,i,null,null,null,null,null,null,null]

This code will work for you. size should be referring to the size of your array while noOfItems refers to the number of items in your array. You were kind of mixing the 2 up. I only changed a couple things in your add() and growBufferIfNecessary().
public class ArrayExpander
{
private int size;
private int noOfItems;
private Object[] store;
private final int INITIALSIZE = 2;
public ArrayExpander()
{
store = new Object[INITIALSIZE];
noOfItems = 0;
size = INITIALSIZE;
}
public void add(Object obj)
{
growBufferIfNecessary();
store[noOfItems++] = obj;
}
public String toString()
{
String temp = "[" + store[0];
for (int i = 1; i < size; i++)
{
temp = temp + "," + store[i];
}
temp = temp + "]";
return temp;
}
private void growBufferIfNecessary()
{
if (noOfItems == size)
{
size = 2 * size;
Object[] newStore = new Object[size];
for (int i = 0; i < store.length; i++)
{
newStore[i] = store[i];
}
store = newStore;
}
}
public static void main(String[] args)
{
ArrayExpander ae = new ArrayExpander();
//System.out.println(ae);
ae.add("a");
ae.add("b");
System.out.println(ae);
ae.add("c");
ae.add("d");
ae.add("e");
ae.add("f");
ae.add("g");
ae.add("h");
System.out.println(ae);
ae.add("i");
System.out.println(ae);
}
}
Try this. If you notice I replaced size in a couple spots with noOfItems. You were really close you just needed to change a couple things.

Manually copying arrays with loops is such a pain, use System.arraycopy(Object,int,Object,int,int) like
private int size = 0;
private Object[] store = new Object[INITIALSIZE];
private void growBufferIfNecessary() {
if (size >= store.length) {
Object[] newStore = new Object[2 * store.length];
System.arraycopy(store, 0, newStore, 0, store.length);
store = newStore;
}
}
I eliminated noOfItems. You don't need it, your add method is just
public void add(Object obj) {
growBufferIfNecessary();
store[size++] = obj;
}
Finally, your toString() could use Arrays.copyOf(T[], int) like
#Override
public String toString() {
return Arrays.toString(Arrays.copyOf(store, size));
}
And then I got your expected output
[a, b]
[a, b, c, d, e, f, g, h]
[a, b, c, d, e, f, g, h, i]

Develop Reference

Java is a programming language and computing platform first released by Sun Microsystems in 1995.

Assign values to array that have multible variables in java - java

Related

How to correctly implement maximum weight independent set of positive tree using BFS

How can I compile this program?

How do I fill an ArrayList with random generated products?

Create a Matrix from an ArrayList

I am getting null values in my Array

Categories

Resources