I am currently prepping to head into a Data Structures Course and as a result have begun reading on certain topics before hand. I am currently studying up on Stacks but have come across a problem.
I am currently coding a Maze App that uses stacks to auto-solve a maze. However, I am experiencing a problem when it comes populating the maze itself.
Code below:
import java.io.*;
import java.util.*;
public class Maze {
private Square move;
private char[][] maze;
private SquareStack s;
private String path =
"C:\\Users\\Sigh\\workspace\\StegmannStackMaze\\maze.txt";
private File file = new File(path);
public Maze(){
s = new SquareStack();
maze = new char[12][12];
}
public void getMaze() throws IOException{
for (int row = 0; row < 12 ; ++row){ // Creates the left/right walls of the maze " | | "
maze[row][0] = '1';
maze[row][11] = '1';
}
for ( int col = 0; col < 12 ; ++col){ // Creates upper and lower walls of the maze
maze[0][col] = '1';
maze[11][col] = '1';
}
Scanner filescan = new Scanner(path);
for( int row = 1; row <= 10 ; ++row){
String line = filescan.nextLine();
String delim = "[ ]+";
String[] tokens = line.split(delim);
for(int col = 1; col <= 10; ++col)
maze[row][col] = tokens[col-1].charAt(0);
}
filescan.close();
}
}
Here is the .txt file
0 0 1 E 1 0 0 1 1 1
0 1 1 0 1 0 1 0 0 0
0 0 0 0 0 0 0 0 1 0
1 1 1 1 1 0 1 1 0 0
0 0 0 1 0 0 0 1 0 1
0 1 0 1 0 1 1 1 0 1
0 1 0 1 0 0 0 1 0 0
1 1 0 1 1 1 0 1 1 0
0 1 0 0 0 0 0 1 1 0
0 1 0 1 1 0 1 0 0 0
The Exception itself occurs at this particular line once col = 2.
for(int col = 1; col <= 10; ++col)
maze[row][col] = tokens[col-1].charAt(0);
}
From what I gather, this line takes each token that is created and populates the column. However, I am not sure why I get a exception.
Thanks for reading and hopefully I can get some insight from you guys.
Changes
Scanner filescan = new Scanner(path);
to
Scanner filescan = new Scanner(file);
The path is a String variable rather than File instance.
Related
So far I have developed a program that uses an adjacency matrix to build a graph using linked implementation.
I'm stuck on how I can read a text file containing an adjacency matrix, and using that data instead of manually inputting the adjacency matrix.
For example, a text file containing the following:
4
0 1 1 0
1 1 1 1
1 0 0 0
1 1 0 1
6
0 1 0 1 1 0
1 0 0 1 1 0
0 0 1 0 0 1
0 0 0 0 1 0
1 0 0 0 0 0
0 0 1 0 0 1
3
0 1 1
1 0 1
1 1 0
You can use this method to read matrix data from file. This method returns a 2d array of bytes containing zeroes and ones.
public static void main(String[] args) throws IOException {
byte[][] matrix = getMatrixFromFile("matrix.txt");
for (int i = 0; i < matrix.length; i++) {
for (int j = 0; j < matrix[i].length; j++) {
System.out.print(matrix[i][j] + ((j + 1) == matrix[i].length ? "" : " "));
}
System.out.println();
}
}
public static byte[][] getMatrixFromFile(String filename) throws IOException {
List<String> lines = Files.readAllLines(Paths.get(filename));
int size = Byte.parseByte(lines.get(0));
byte[][] matrix = new byte[size][size];
for (int i = 1; i < lines.size(); i++) {
String[] nums = lines.get(i).split(" ");
for (int j = 0; j < nums.length; j++) {
matrix[i - 1][j] = Byte.parseByte(nums[j]);
}
}
return matrix;
}
Here I am assuming the file will contain data for one matrix, like following, but my code can easily be extended to read data for multiple matrices and return a list of 2d byte array.
4
0 1 1 0
1 1 1 1
1 0 0 0
1 1 0 1
I've been working on a program to implement a DFS in Java (by taking an adjacency matrix as input from a file). Basically, assuming vertices are traveled in numerical order, I would like to print the order that vertices become dead ends, the number of connected components in the graph, the tree edges and the back edges. But I'm not completely there yet. When I run my program, I get the number "1" as output, and nothing more. I've tried debugging certain parts of the DFS class, but I still can't quite figure out where I'm going wrong. Here is my code:
A basic "Driver" class:
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Driver {
public static void main(String[] args) throws FileNotFoundException {
Scanner scanner = new Scanner(new File("sample1.txt"));
scanner.useDelimiter("[\\s,]+");
int input = scanner.nextInt();
int[][] adjMatrix = new int[8][8];
for(int i=0; i < input; i++) {
for (int j=0; j < input; j++) {
adjMatrix[i][j] = scanner.nextInt();
}
}
scanner.close();
new DFS(adjMatrix);
}
}
DFS class:
import java.util.Stack;
public class DFS {
Stack<Integer> stack;
int first;
int[][] adjMatrix;
int[] visited = new int[7];
public DFS(int[][] Matrix) {
this.adjMatrix = Matrix;
stack = new Stack<Integer>();
int[] node = {0, 1, 2, 3, 4, 5, 6};
int firstNode = node[0];
depthFirstSearch(firstNode, 7);
}
public void depthFirstSearch(int first,int n){
int v,i;
stack.push(first);
while(!stack.isEmpty()){
v = stack.pop();
if(visited[v]==0) {
System.out.print("\n"+(v+1));
visited[v]=1;
}
for (i=0;i<n;i++){
if((adjMatrix[v][i] == 1) && (visited[i] == 0)){
stack.push(v);
visited[i]=1;
System.out.print(" " + (i+1));
v = i;
}
}
}
}
}
And the matrix from the input file looks like this:
0 1 0 0 1 1 0 0
1 0 0 0 0 1 1 0
0 0 0 1 0 0 1 0
0 0 1 0 0 0 0 1
1 0 0 0 0 1 0 0
1 1 0 0 1 0 0 0
0 1 1 0 0 0 0 1
0 0 0 1 0 0 1 0
Take a look at this part:
int input = scanner.nextInt();
int[][] adjMatrix = new int[8][8];
for(int i=0; i < input; i++) {
for (int j=0; j < input; j++) {
adjMatrix[i][j] = scanner.nextInt();
}
}
First you read a number, input.
Then you read input rows, in each row input columns.
This is your input data:
0 1 0 0 1 1 0 0
1 0 0 0 0 1 1 0
0 0 0 1 0 0 1 0
0 0 1 0 0 0 0 1
1 0 0 0 0 1 0 0
1 1 0 0 1 0 0 0
0 1 1 0 0 0 0 1
0 0 0 1 0 0 1 0
What is the first number, that will be read by scanner.nextInt().
It's 0. So the loop will do nothing.
Prepend the number 8 to your input, that is:
8
0 1 0 0 1 1 0 0
1 0 0 0 0 1 1 0
0 0 0 1 0 0 1 0
0 0 1 0 0 0 0 1
1 0 0 0 0 1 0 0
1 1 0 0 1 0 0 0
0 1 1 0 0 0 0 1
0 0 0 1 0 0 1 0
Btw, it's a good idea to verify that you have correctly read the matrix.
Here's an easy way to do that:
for (int[] row : adjMatrix) {
System.out.println(Arrays.toString(row));
}
There are several other issues in this implementation:
The number 7 appears in a couple of places. It's actually a crucial value in the depth-first-search algorithm, and it's actually incorrect. It should be 8. And it should not be hardcoded, it should be derived from the size of the matrix.
It's not a good practice to do computation in a constructor. The purpose of a constructor is to create an object. The depth-first-logic could be moved to a static utility method, there's nothing in the current code to warrant a dedicated class.
Fixing the above issues, and a few minor ones too, the implementation can be written a bit simpler and cleaner:
public static void dfs(int[][] matrix) {
boolean[] visited = new boolean[matrix.length];
Deque<Integer> stack = new ArrayDeque<>();
stack.push(0);
while (!stack.isEmpty()) {
int v = stack.pop();
if (!visited[v]) {
System.out.print("\n" + (v + 1));
visited[v] = true;
}
for (int i = 0; i < matrix.length; i++) {
if (matrix[v][i] == 1 && !visited[i]) {
visited[i] = true;
stack.push(v);
v = i;
System.out.print(" " + (i + 1));
}
}
}
}
I'm reading in numbers to fill an adjacency matrix. The numbers are read in from a file and the format can be seen below.
0 1 0 0 1 1 0 0
1 0 0 0 0 1 1 0
0 0 0 1 0 0 1 0
0 0 1 0 0 0 0 1
1 0 0 0 0 1 0 0
1 1 0 0 1 0 0 0
0 1 1 0 0 0 0 1
0 0 0 1 0 0 1 0
But I'm getting an InputMismatchException when I try to run my program, and I can't figure out why. My code is below. I'd greatly appreciate some help.
import java.util.Scanner;
public class Driver {
public static void main(String[] args) {
Scanner scanner = new Scanner("sample1.txt");
scanner.useDelimiter("[\\s,]+");
int input = scanner.nextInt();
int[][] adjMatrix = new int[8][8];
for(int i=0; i < input; i++) {
for (int j=0; j < input; j++) {
adjMatrix[i][j] = scanner.nextInt();
}
}
scanner.close();
new DFS(adjMatrix);
}
}
I need to create a 2D array from a text file for later use in some operations.
This is my file separated by a space" ":
0 1 0 1 0 1 0 1 0 1
1 0 1 0 1 0 1 0 1 0
0 1 0 1 0 1 0 1 0 1
1 0 1 0 1 0 1 0 1 0
0 1 0 1 0 1 0 1 0 1
1 0 1 0 1 0 1 0 1 0
0 1 0 1 0 1 0 1 0 1
1 0 1 0 1 0 1 0 1 0
0 1 0 1 0 1 0 1 0 1
1 0 1 0 1 0 1 0 1 0
And this is the code that I have:
import java.io.*;
public class TxtToArray{
public static void main(String args[]){
double[][] array = new double[100][100];
int x=0, y=0;
try{
BufferedReader in = new BufferedReader(new FileReader("E:\\Documents\\JavaPrograms\\TxtToArray\\src\\Array.txt"));
String bar;
while ((bar = in.readLine()) != null){
String[] values = bar.split(" ");
for (String str : values){
double str_double = Double.parseDouble(str);
array[x][y]=str_double;
y++;
}
x++;
}
in.close();
}catch( IOException ioException ) {
System.out.println("Something happened...");
}
}
}
Thanks! for the help
EDIT:
I have corrected some errors in what came to be the explanation and code syntax. If there are more let me know.
You never told us what the problem is, but one issue I see is that you are splitting each line of input on comma alone. This won't work because your input data also uses space as a delimeter. One option is to remove this whitespace before splitting by comma:
while ((bar = in.readLine()) != null) {
String[] values = bar.replaceAll("\\s+", "")
.split(",");
for (int y=0; y < values.length; ++y) {
double str_double = Double.parseDouble(values[y]);
array[x][y] = str_double;
}
x++;
}
You will notice that I used a for loop to iterate over the strings in each input. This is a nice option because it eliminates the need for you to manage the second index of your array.
Your numers in the file are not only seperated by ,, but also by whitespaces. Double.parseDouble throws an exception, if this whitespace is included in the parameter. Therefore you need to use a regex that also matches these chars too, e.g. ,\s*. Also you need to set y back to 0 at the beginning of every iteration of the while loop:
while ((bar = in.readLine()) != null){
String[] values = bar.split(",\\s*");
y = 0;
for (String str : values){
double str_double = Double.parseDouble(str);
array[x][y] = str_double;
y++;
}
x++;
}
I'm trying to get an output of a random string consisted of 1's and 0's in a Matrix style. I know how to display a string consisted of 1's and 0's, but I can't keep on looping through it for some reason. What I'm trying to do, is that whenever the StringBuilder reaches the length of 20, I want to start the loop on a new line again and repeat this 100 times.
import java.util.List;
import java.util.Random;
public class main {
static Random rand = new Random();
static StringBuilder x = new StringBuilder();
static int a = 0;
public static void main(String[] args) {
generatingnumber();
}
public static void generatingnumber() {
for (int bv = 0; bv <= 100; bv++) {
int random = rand.nextInt(50);
if (random % 2 == 0) {
x.append(" 0");
} else {
x.append(" 1");
}
if (x.length() == 20) {
System.out.println(x);
}
}
}
}
public class MatrixFilm {
public static void main(String[] args) {
int rows = 100;
int cols = 20;
for (int count1 = 0; count1 < (rows * cols); count1++) {
for (int count2 = 0; count2 < cols; count2++) {
int randomNum = 0 + (int) (Math.random() * 2);
System.out.print(" " + randomNum);
}
System.out.println();
}
}
}
Result:
0 0 1 0 0 0 0 1 0 0 1 1 0 0 1 0 1 1 1 1
1 1 0 1 1 1 0 1 0 1 0 1 1 0 1 1 0 0 1 0
0 1 0 0 1 0 1 1 0 0 1 1 1 0 1 1 1 1 1 0
0 1 0 1 1 1 1 1 0 0 1 1 0 0 0 1 1 0 1 0
0 0 0 1 0 1 0 0 1 0 0 0 1 0 1 0 0 1 0 0
....
Your string has length of 20 characters only once. You are not interested in whether x.length() == 20 but if x.length() % 20 == 0.
For a new line you can append "\n" (or "\r\n" for Windows machine) to the string, everytime just before printing it.
Change println to print (which doesn't add new line character at the end of printed string) in order to maintain continuity between prints.
Taking all into account:
if (x.length() % 20 == 0) {
x.append("\r\n");
System.out.print(x);
}
However it still wouldn't be enough, for "\r\n" itself adds to the length of the string. This should work:
if (x.length() % 20 == 0) {
x.replace(x.length() - 2, x.length(), "\r\n");
System.out.print(x);
}
You can also - and it would be better to... - reset the string, as #owlstead has mentioned.
if (x.length() == 20) {
System.out.println(x);
x.setLength(0);
}
Anyway; what I presented is not a solution for the problem. Only solution to - probably improper - approach you have currently taken on it.