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What causes a java.lang.ArrayIndexOutOfBoundsException and how do I prevent it?
(26 answers)
Closed 3 years ago.
My sudoku solver replaces "-" with zeros, then solves the puzzle. It works for most puzzles that I've tried, but throws an ArrayIndexOutOfBoundsException for puzzles with a full row of dashes. I've tried tweeking different things to get it to work, but I'm a little lost.
This is what the puzzle looks like.
public static int[][] theArray = new int [9][9];
public static int SIZE = 9;
private static boolean isCompletePuzzle() {
// checks for 0 in rows/cols
for (int i = 0; i <= SIZE; i++) {
for (int j = 0; j <= SIZE; j++) {
if (theArray[i][j] != 0) {
return true;
}
}
}
return false;
}
private static boolean isValidPuzzle(int row, int col, int number) {
// checks rows
for (int i = 0; i < SIZE; i++) {
if (theArray[row][i] == number) {
return true;
}
}
// checks columns
for (int i = 0; i < SIZE; i++) {
if (theArray[i][col] == number) {
return true;
}
}
// checks 3x3
int r = row - row % 3;
int c = col - col % 3;
for (int i = r; i < r + 3; i++)
for (int j = c; j < c + 3; j++)
if (theArray[i][j] == number)
return true;
return false;
}
private static boolean isSolvedPuzzle(int row, int col, int number) {
if (isValidPuzzle(row, col, number) == true && isCompletePuzzle() == true) {
return true;
}
return false;
}
public static boolean solvePuzzle() {
for (int row = 0; row < SIZE; row++) {
for (int col = 0; col < SIZE; col++) {
if (theArray[row][col] == 0) {
for (int number = 1; number <= SIZE; number++) {
if (!isSolvedPuzzle(row, col, number)) {
theArray[row][col] = number;
if (solvePuzzle()) {
return true;
}
else {
theArray[row][col] = 0;
}
}
}
return false;
}
}
}
return true;
}
in ur isCompletePuzzle() function ur loop conditions i <= SIZE and j <= SIZE cause ArrayIndexOutOfBoundsException
when i is 9 the if (theArray[i][j] != 0) throw ArrayIndexOutOfBoundsException
Related
This program working quite well. i wrote some exception ex N=1,2 and find others.
I have a problem with a bord part when I give a number above 30 program waiting and freezing how can I solve that? I want to write for at least 255 or 150(max value). in there if N=30 or more program will stop when you want to run.
package com.company;
import java.util.Scanner;
public class NQueenProblem {
Scanner scanner = new Scanner(System.in);
final int N = Integer.valueOf(scanner.nextLine());
void printSolution(int board[][]) {
for (int i = 0; i < N; i++) {
for (int j = 0; j < N; j++)
System.out.print(" " + board[i][j]
+ " ");
System.out.println();
}
}
safe condition is working correctly in big boards
boolean isSafe(int board[][], int row, int col) {
int i, j;
for (i = 0; i < col; i++)
if (board[row][i] == 1)
return false;
for (i = row, j = col; i >= 0 && j >= 0; i--, j--)
if (board[i][j] == 1)
return false;
for (i = row, j = col; j >= 0 && i < N; i++, j--)
if (board[i][j] == 1)
return false;
return true;
}
boolean solveNQUtil(int board[][], int col) {
if (col >= N)
return true;
for (int i = 0; i < N; i++) {
if (isSafe(board, i, col)) {
board[i][col] = 1;
if (solveNQUtil(board, col + 1) == true)
return true;
board[i][col] = 0;
}
}
return false;
}
boolean solveNQ() {
int board[][]=new int[N][N];
if (solveNQUtil(board, 0) == false) {
System.out.print("Solution does not exist");
return false;
}
printSolution(board);
return true;
}
// driver program to test above function
public static void main(String args[]) {
NQueenProblem Queen = new NQueenProblem();
Queen.solveNQ();
}
}
I have no idea what the problem is .I printed the moveVal all the time it prints 0 and its going in a horizontal order.
The I have been editing a changing the code by using Google and YouTube but, there was no good
static class Move {
int row, col;
}
private boolean equals(JButton a, JButton b, JButton c){
return a.getText().equals(b.getText()) && b.getText().equals(c.getText()) && !a.getText().equals("");
}
private boolean isGameOver() {
for (int i = 0; i < 3; i++) {
if (equals(board[i][0], board[i][1], board[i][2])) {
return true;
}
}
for (int i = 0; i < 3; i++) {
if (equals(board[0][i], board[1][i], board[2][i])) {
return true;
}
}
if (equals(board[0][0], board[1][1], board[2][2])) {
return true;
}
else if (equals(board[2][0], board[1][1], board[0][2])) {
return true;
}
int openSpots = 0;
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
if (board[i][j].getText().equals("")) {
openSpots++;
}
}
}
return openSpots == 0;
}
private int evaluate(JButton[][] b) {
for (int row = 0; row < 3; row++)
{
if (b[row][0] == b[row][1] &&
b[row][1] == b[row][2])
{
if (b[row][0].getText().equals(ai))
return 20;
else if (b[row][0].getText().equals(human))
return -10;
}
}
for (int col = 0; col < 3; col++)
{
if (b[0][col] == b[1][col] &&
b[1][col] == b[2][col])
{
if (b[0][col].getText().equals(ai))
return 20;
else if (b[0][col].getText().equals(human))
return -10;
}
}
if (b[0][0] == b[1][1] && b[1][1] == b[2][2])
{
if (b[0][0].getText().equals(ai))
return 20;
else if (b[0][0].getText().equals(human))
return -10;
}
if (b[0][2] == b[1][1] && b[1][1] == b[2][0])
{
if (b[0][2].getText().equals(ai))
return 20;
else if (b[0][2].getText().equals(human))
return -10;
}
return 0;
}
private int minimax(JButton[][] position, int depth, boolean isMax) {
if (isGameOver() || depth == 0){
return evaluate(position);
}
else if (isMax)
{
int best = -1000000000;
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
if (position[i][j].getText().equals(""))
{
position[i][j].setText(ai);
JButton[][] position1 = position;
best = Math.max(best, minimax(position1, depth - 1, false));
System.out.println(best);
position[i][j].setText("");
}
}
}
return best;
}
else
{
int best1 = 1000000000;
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
if (position[i][j].getText().equals(""))
{
position[i][j].setText(human);
JButton[][] position1 = position;
best1 = Math.min(best1, minimax(position1, depth - 1, true));
position[i][j].setText("");
}
}
}
return best1;
}
}
private void BestMove(JButton[][] board) {
int bestVal = -1000000000;
Move bestMove = new Move();
bestMove.row = -1;
bestMove.col = -1;
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
if (board[i][j].getText().equals(""))
{
board[i][j].setText(ai);
int moveVal = minimax(board, 3, false);
board[i][j].setText("");
if (moveVal > bestVal)
{
bestVal = moveVal;
bestMove.row = i;
bestMove.col = j;
}
}
}
}
board[bestMove.row][bestMove.col].setText(ai);
playersTurn = true;
CheckWinner();
}
Any ideas & please help is needed
past 3 days I have been debugging I know this code is not the best in fact this code might be the worst you have ever seen.
Blockquote
You have only 3 possible evaluations:
20, if the AI wins
-10, if the human wins
0, in all other cases
As you only look at 4 turns (ai, human, ai, human), it's impossible to find a winning position, so the evaluation is always 0.
There is no obvious issue with your implementation of the minimax, however your evaluation function is too simple.
You can, for example:
Give more points to playing in a position that creates a row of 2
Give more points to playing in a position that creates multiple rows of 2
Give less points to a position that is already blocked
However, there is only so much you can do. This game is obviously solved, and a perfect player can always get a draw playing either sides.
I am making a Sudoku game in Java and I need some help.
I've got two classes for generating the Sudoku puzzle: SudokuSolver, SudokuGenerator`.
The SudokuSolver creates a full valid Sudoku puzzle for an empty table and the SudokuGenerator removes a random value from the table and then checks (using SudokuSolver) if the Sudoku puzzle is unique.
I found out that the Sudoku puzzle isn't unique, so I think my algorithm for checking the uniqueness of the Sudoku puzzle is bad.
For example, I have this Sudoku puzzle
497816532
132000000
000000000
910600080
086009000
000084963
021063059
743050020
600278304
And this solution:
497816532
132**745**698
568392471
914**637**285
386529147
275184963
821463759
743951826
659278314
I went to https://www.sudoku-solutions.com/ and I added the pattern of my Sudoku and they gave me another solution:
497816532
132**547**698
568392471
914**635**287
386729145
275184963
821463759
743951826
659278314
The funny think is that they're saying that This puzzle is valid and has a unique solution.
Some opinions?
SudokuSolver
public class SudokuSolver {
public static final int GRID_SIZE = 9;
public static final int SUBGRID_SIZE = 3;
private static int validRow = 0;
private static int validCol = 0;
private int[] nums = {1, 2, 3, 4, 5, 6, 7, 8, 9};
public boolean solveSudoku(int[][] values, int forbiddenNum) {
if(!findUnassignedLocation(values)) return true;
//suffle the nums array - for having a different valid sudoku
shuffleNums();
for (int i = 0; i < GRID_SIZE; i++) {
int num = nums[i];
if(num == forbiddenNum) continue; //
if(isSafe(values,validRow, validCol, num)) {
values[validRow][validCol] = num;
if(solveSudoku(values, forbiddenNum)) return true;
if(validCol == 0) {
validRow--;
validCol = 8;
}else{
validCol--;
}
values[validRow][validCol] = 0;
}
}
return false;
}
public boolean createValidSudoku(int[][] values) {
if(!findUnassignedLocation(values)) return true;
shuffleNums();
for (int i = 0; i < GRID_SIZE; i++) {
int num = nums[i];
if(isSafe(values,validRow, validCol, num)) {
values[validRow][validCol] = num;
if(createValidSudoku(values)) return true;
if(validCol == 0) {
validRow--;
validCol = 8;
}else{
validCol--;
}
values[validRow][validCol] = 0;
}
}
return false;
}
private void shuffleNums() {
Random random = new Random();
for(int i = nums.length - 1; i > 0; i--) {
int index = random.nextInt(i + 1);
int a = nums[index];
nums[index] = nums[i];
nums[i] = a;
}
}
private boolean findUnassignedLocation(int[][] values) {
for(int row = 0; row < GRID_SIZE; row++) {
for(int col = 0; col < GRID_SIZE; col++) {
if (values[row][col] == 0) {
validRow = row;
validCol = col;
return true;
}
}
}
return false;
}
private boolean usedInRow(int[][] values, int row, int num) {
for (int col = 0; col < GRID_SIZE; col++) {
if(values[row][col] == num) return true;
}
return false;
}
private boolean usedInCol(int[][] values, int col, int num) {
for (int row = 0; row < GRID_SIZE; row++) {
if(values[row][col] == num) return true;
}
return false;
}
private boolean usedInBox(int[][] values, int boxStartRow, int boxStartCol, int num) {
for(int row = 0; row < SUBGRID_SIZE; row++) {
for (int col = 0; col < SUBGRID_SIZE; col++) {
if (values[row + boxStartRow][col + boxStartCol] == num) return true;
}
}
return false;
}
private boolean isSafe(int[][] values,int row, int col, int num) {
return !usedInRow(values, row, num) &&
!usedInCol(values, col, num) &&
!usedInBox(values, row - row % 3, col - col % 3, num);
}
public void printGrid(int[][] values) {
for (int row = 0; row < GRID_SIZE; row++) {
for (int col = 0; col < GRID_SIZE; col++) {
System.out.print(values[row][col]);
}
System.out.println();
}
}
}
SudokuGenerator
public class SudokuGenerator {
private int[][] generatorValues = new int[9][9];
public void generateSudoku() {
SudokuSolver sudokuSolver = new SudokuSolver();
//generate a random valid sudoku for an empty table
sudokuSolver.createValidSudoku(generatorValues);
int count = 0;
printNums(generatorValues);
while(count < 40){
Random random = new Random();
int row = 0;
int col = 0;
if(count < 15){
row = random.nextInt(3);
col = random.nextInt(9);
} else if (count >= 15 && count < 30) {
row = random.nextInt(3) + 3;
col = random.nextInt(9);
}else {
row = random.nextInt(3) + 6;
col = random.nextInt(9);
}
int num = generatorValues[row][col];
int tempValues[][] = Arrays.copyOf(generatorValues, generatorValues.length);
//System.out.println("Row:" + row + "Col: " + col + "Num: " + num);
//Set the cell to 0;
if(generatorValues[row][col] != 0){
generatorValues[row][col] = 0;
} else{
continue;
}
//If found a solution, set cell back to original num
if(sudokuSolver.solveSudoku(tempValues, num)) {
generatorValues[row][col] = num;
continue;
}
count++;
}
System.out.println("------------------");
printNums(generatorValues);
}
private void printNums(int[][] values) {
for (int row = 0; row < 9; row++) {
for(int col = 0; col < 9; col++) {
System.out.print(values[row][col]);
}
System.out.println();
}
}
public int[][] getGeneratorValues () {
return generatorValues;
}
}
I'm trying to code a method which checks for duplicates on my Sudoku board. Currently, my method getFrontier() always returns true, and I've come to learn that it's because it's only checking for one value rather than an array or values. I use the method 3 times in squareCheck(), rowCheck() and columnCheck(). Is there any way to code the method so it would retain the previous value which was input and then check it against the new value?
My current code:
public class validCheck {
public boolean isSolved(int[][][] board)
{
for(int index = 0; index < board.length;index++)
{
for(int r = 0; r < board[0].length; r++)
{
for(int c = 0; c < board[0].length;c++)
{
if(board[index][r][c] == 0)
return false;
}
}
}
return true;
}
public boolean getFrontier(int value)
{
Set<Integer> reserve = new HashSet<>();
for(int n = 1; n < 10; n++)
{
if(value == n && reserve.contains(n))
return false;
else if(value == n) reserve.add(n);
}
return true;
}
public boolean squareCheck(int[][][] board, int index)
{
for(int r = 0; r < board[0].length; r++)
{
for(int c = 0; c < board[0].length; c++)
{
if(!getFrontier(board[index][r][c]))
{
System.out.println("Square error at ["+index + r + c +"]");
return false;
}
}
}
return true;
}
public boolean isValid(int[][][] board)
{
if(isSolved(board))
{
for(int i = 0; i < board.length; i++)
{
for(int r = 0; r < board[0].length;r++)
{
for(int c = 0; c < board[0].length;c++)
{
if(!rowCheck(board,i,r) || !columnCheck(board,i,c) || !squareCheck(board,i))
{
return false;
}
}
}
}
}
return true;
}
public boolean columnCheck(int[][][] board, int index, int col)
{
int target = 0;
if(index <=2)
{
target = index + 6;
}
else if(index > 2 && index < 6)
{
target = index +3;
index = index - 3;
}
else if (index > 5)
{
target = index;
index = index - 6;
}
while(index <= target)
{
for(int r = 0; r < board[0].length;r++)
{
if(!getFrontier(board[index][r][col]))
{
System.out.println("Column error at " + index + r + col);
return false;
}
}
index = index + 3;
}
return true;
}
public boolean rowCheck(int[][][] board, int index, int row)
{
int target = 0;
if(index <= 2)
{
index = 0;
target = 2;
}
else if (index <= 5)
{
index = 3;
target = 5;
}
else if(index <= 8)
{
index = 6;
target = 8;
}
while(index <= target)
{
for(int c = 0; c < board[0].length; c++)
{
if(!getFrontier(board[index][row][c]))
{
System.out.println("Row error at "+index+row+c);
return false;
}
}
index++;
}
return true;
}
}
Usage:
public static void main(String[] args) {
int[][][] solved = {{{5,3,4},{6,7,2},{1,9,8}},
{{6,7,8},{1,9,5},{3,4,2}},
{{9,1,2},{3,4,8},{5,6,7}},
{{8,5,9},{4,2,6},{7,1,3}},
{{7,6,1},{8,5,3},{9,2,4}},
{{4,2,3},{7,9,1},{8,5,6}},
{{9,6,1},{2,8,7},{3,4,5}},
{{5,3,7},{4,1,9},{2,8,6}},
{{2,8,4},{6,3,5},{1,7,9}}};
validCheck checker = new validCheck();
if(checker.isValid(solved))
System.out.println(true);
else System.out.println(false);
}
Any help will be greatly be appreciated!!!
Here is what I would do to find a valid board config in a 2D sudoku board. I would use a HashSet for a row and another for the column, as long as we never encounter repeats and the values contain 1 to the length of the array we know the board is valid.
int [][] board = {{1,2,3},
{2,3,1},
{3,1,2}
};
HashSet<Integer> rowDuplicates = new HashSet<>();
HashSet<Integer> colDuplicates = new HashSet<>();
boolean invalidBoard = false;
for(int i = 0 ; i < board.length; i++)
{
for(int j = 0; j < board[i].length; j++)
{
if(rowDuplicates.contains(board[i][j]) || colDuplicates.contains(board[j][i]))
{
//this board is not valid
invalidBoard = true;
}
else
{
rowDuplicates.add(board[i][j]);
colDuplicates.add(board[j][i]);
}
}
//now check they contain the correct numbers from 1 to the size of the array
if(colDuplicates.size() == rowDuplicates.size())
{
for(int index = 0; index < colDuplicates.size(); index++)
{
if(!(colDuplicates.contains(index + 1) && rowDuplicates.contains(index + 1)))
{
invalidBoard = true;
break;
}
}
}
else
{
invalidBoard = true;
}
colDuplicates.clear();
rowDuplicates.clear();
}
System.out.println("invalid board: " + invalidBoard);
You should be able to expand this to your 3D array but you can see how much easier it is to use HashSets to verify a valid 2D array Sudoku board.
Closed. This question is not reproducible or was caused by typos. It is not currently accepting answers.
This question was caused by a typo or a problem that can no longer be reproduced. While similar questions may be on-topic here, this one was resolved in a way less likely to help future readers.
Closed 8 years ago.
Improve this question
I was trying to solve the Game of life problem for a teacher. Rules of that game are:
Any live cell with fewer than two live neighbors dies, as if caused by under-population. Any live cell with two or three live neighbors’ lives on to the next generation. Any live cell with more than three live neighbors dies, as if by overcrowding. Any dead cell with exactly three live neighbors becomes a live cell, as if by reproduction.
There are two problems with my code - first of all, my main class doesn't seem to be working. Secondly, I performed the problem through many many if else statements. Are there more concise ways of writing the exceptions for my getNeighbors() method?
Thanks!
import java.util.Random;
public class GameOfLife {
final static int ROWS = 6;
final static int COLUMNS = 7;
String[][] simulator;
private Random randomGenerator;
public GameOfLife() {
simulator = new String[ROWS][COLUMNS];
randomGenerator = new Random();
}
public void fillSpot (int row, int column) {
simulator [row][column] = "O";
}
private void deleteSpot (int row, int column) {
simulator[row][column] = "";
}
// Do I need the above methods? really?
public void randomSimulation() {
for (int i = 0; i <= ROWS; i++) {
for (int j = 0; j <= COLUMNS; j++) {
int random = randomGenerator.nextInt(1);
if (random == 1) {
fillSpot(i,j);
}
}
}
}
private void getNeighbors (int row, int column) {
int neighbors = 0;
if (row < ROWS && row > 0 && column < COLUMNS && column > 0) {
for (int i = row - 1; i <= row + 1; i++) {
for (int j = column - 1; j <= column + 1; j++) {
String temp = simulator[i][j];
if (temp.contains("O")) {
neighbors++;
}
}
}
}
if (row > ROWS || column > COLUMNS || row < 0 || column < 0) {
}
else if (row == ROWS && column < COLUMNS && column != 0) {
for (int i = row - 1; i <= ROWS; i++) {
for (int j = column - 1; j <= column + 1; j++) {
String temp = simulator[i][j];
if (temp.contains("O")) {
neighbors++;
}
}
}
}
else if (row < ROWS && column == COLUMNS && row != 0) {
for (int i = row - 1; i <= row + 1; i++) {
for (int j = column - 1; j <= COLUMNS; j++) {
String temp = simulator[i][j];
if (temp.contains("O")) {
neighbors++;
}
}
}
}
else if (row == 0 && column < COLUMNS && column != 0) {
for (int i = 0; i <= row + 1; i++) {
for (int j = column - 1; j <= COLUMNS + 1; j++) {
String temp = simulator[i][j];
if (temp.contains("O")) {
neighbors++;
}
}
}
}
else if (row == 0 && column == COLUMNS) {
for (int i = row; i <= row + 1; i++) {
for (int j = column - 1; j <=COLUMNS; j++) {
String temp = simulator[i][j];
if (temp.contains("O")) {
neighbors++;
}
}
}
}
else if (column == 0 && row < ROWS && row != 0) {
for (int i = row - 1; i <= row + 1; i++) {
for (int j = column; j <= COLUMNS + 1; j++) {
String temp = simulator[i][j];
if (temp.contains("O")) {
neighbors++;
}
}
}
}
else {
for (int i = row; i <= row + 1; i++) {
for (int j = column; j <= column + 1; j++) {
String temp = simulator[i][j];
if (temp.contains("O")) {
neighbors++;
}
}
}
}
// for row == 0 && column == 0
if (simulator [row][column].contains("O")) {
neighbors--;
}
simulator[row][column] += " " + neighbors;
}
//There are wayyy too manyy clauses here for me to be comfortable. There's got to be a way to do this cleaner
private void nextGenPlanning() {
for (int i = 0; i <= ROWS; i++) {
for (int j = 0; j <= COLUMNS; j++) {
getNeighbors(i,j);
}
}
}
private void nextGen() {
nextGenPlanning();
for (int i = 0; i <= ROWS; i++) {
for (int j = 0; j <= COLUMNS; j++) {
String temp = simulator[i][j];
if (temp.charAt(temp.length()) <= 1 || temp.charAt(temp.length()) >= 4) {
deleteSpot(i,j);
}
else {
fillSpot (i,j);
}
}
}
}
public String toString() {
String string = "";
for (int i = 0; i < ROWS; i++) {
string = string + "|";
for (int j = 0; j < COLUMNS; j++) {
String temp = simulator[i][j];
string = string + temp.charAt(0);
}
string = string + "|\n";
}
return string;
}
public String simulate (int numOfTrials) {
String string = "";
for (int i = 0; i <= numOfTrials; i++) {
nextGen();
string += toString();
}
return string;
}
public void main (String [] args) {
randomSimulation();
System.out.println(simulate(2));
}
}
First, you have:
public void main (String [] args) {
randomSimulation();
System.out.println(simulate(2));
}
You should have:
public static void main (String[] args) {
GameOfLife game = new GameOfLife();
game.randomSimulation();
System.out.println(game.simulate(2));
}
Second, for getNeighbors, first consider that a 'get' method usually returns a value. If you're counting the number of neighbors, consider:
public int getNeighbors(int x, int y) {
int neighbors = 0;
int leftX = Math.max(x-1, 0);
int rightX = Math.min(x+1, COLUMNS);
int topY = Math.max(y-1, 0);
int bottomY = Math.min(y+1, ROWS);
for (int i=leftX; i < rightX; i++) {
for (int j=topY; j < bottomY; j++) {
if (simulator[i][j].contains('O')) { // Notice I'm using a char here, see my next comment
neighbors++;
}
}
}
return neighbors;
}
Third, I recommend using char[][] instead of String[][] for your simulator if each space in the simulator only holds one character value. There are some things about Strings in Java that you don't need to get tripped up with - for example, in Java, you cannot compare the value of Strings using == (you need to use String's equals() method).
First , your main class should be Public static void main(String[] args) and you can use switch case except of if else if you really sure on if else you can use if ( blabla == blablabla &(this means and ) blaba == babalaba)