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Finding the number of areas of true values in a 2D array

I have a question about my homework in scratching my head-on.
So I need to build a program that counts the number of areas of true value (near to each other) in the 2D array.
{0,1,0,0}
{1,0,0,1}
{1,1,0,1}
{1,0,0,1}
So the program needs to return 3 because there 3 places with trues.
If there are no true then to return 0.
The program needs to recursive and without loops.
Thanks in advance to the ones that will help me solve this one. I didn't even have any idea how to start it.

Ok, you do a dfs to record the cells you went and you can have a boolean[][] to record the cells you went. Then you just loop through the grid to see where you have not gone. If you did not go there yet, go there and also perform a dfs on nearby cells, but anyway, a code would be more clear.
public static int[][] grid;
public static boolean[][] went;
public static int r, c;
public static void dfs(int x, int y) {
if (x < 0 || x >= r || y < 0 || y >= c) {//out of the grid
return;
}
if (went[x][y]) {//I went here
return;
}
went[x][y] = true;
if (grid[x][y] == 0) {//It's false here so don't go
return;
}
dfs(x - 1, y);
dfs(x + 1, y);
dfs(x, y - 1);
dfs(x, y + 1);
}
public static void main(String[] args) throws IOException {
BufferedReader input =
new BufferedReader(new InputStreamReader(System.in));
StringTokenizer st = new StringTokenizer(input.readLine());
//input reading
r = Integer.parseInt(st.nextToken());
c = Integer.parseInt(st.nextToken());
grid = new int[r][c];
went = new boolean[r][c];
for (int i = 0; i < r; i++) {
st = new StringTokenizer(input.readLine());
for (int j = 0; j < c; j++) {
grid[i][j] = Integer.parseInt(st.nextToken());
}
}
//end of input reading
int cnt = 0;//number of areas
for (int i = 0; i < r; i++) {
for (int j = 0; j < c; j++) {
// If I have not went have and the value
// must be true so I would perform a dfs
// (since I only care about the value of 1s)
if (!went[i][j] && grid[i][j] == 1) {
cnt++;//add to our counter
dfs(i, j);//have not went here
}
}
}
System.out.println(cnt);
}

This solution uses the only recursion. No loops.
public static void main(String... args) {
System.out.println(countTrueAreas(new int[][] {
{ 0, 1, 0, 0 },
{ 1, 0, 0, 1 },
{ 1, 1, 0, 1 },
{ 1, 0, 0, 1 } })); // 3
}
public static int countTrueAreas(int[][] grid) {
return countTrueAreas(grid, 0, 0, 10) - 10;
}
private static int countTrueAreas(int[][] grid, int row, int col, int num) {
if (row == grid.length)
return num;
if (col == grid[row].length) {
if (++row == grid.length)
return num;
col = 0;
}
if (grid[row][col] == 1)
dfs(grid, row, col, num++);
return countTrueAreas(grid, row, col + 1, num);
}
private static void dfs(int[][] grid, int row, int col, int num) {
if (row < 0 || row >= grid.length)
return;
if (col < 0 || col >= grid[row].length)
return;
if (grid[row][col] != 1)
return;
grid[row][col] = num;
dfs(grid, row, col - 1, num);
dfs(grid, row, col + 1, num);
dfs(grid, row - 1, col, num);
dfs(grid, row + 1, col, num);
}

Making a java 2048 game, upon sliding it goes through the loop more times than it should and hits tests/alters numbers already altered

So I have a solid slide function, the problem is (which is very hard to explain!) it goes through all the possibilities including spaces in the 2d array that have already been added together: say there is a setup like this: 4,4,8,2 ---after one swipe to the right, it ends up like this: ,_,16,2. however in the actual game, after one swipe right, it should look like this: ___,8,2.
Basically, how can I fix this? You don't need to tell me the code, it's my project for my final, but I'd like to get some sort of explanation as to why this is happening.
I've attempted to loop through the array from right to left but that resulted in the numbers not even moving.
processUserChoice(String i) {
if (i.equals("d")) {
while ((slideRight())) {
moveRight();
}
}
printBoard();
}
public boolean slideRight() {
for (int i = 0; i < board.length; i++) {
for (int j = 0; j < board[i].length - 1; j++) {
if (board[i][j + 1] == 0 && board[i][j] != 0) {
return true;
} else if (board[i][j + 1] == board[i][j] && board[i][j] != 0) {
return true;
}
}
}
return false;
}
public void moveRight() {
for (int i = 0; i < board.length; i++) {
for (int j = 0; j < board[i].length - 1; j++) {
if (board[i][j + 1] == 0 && board[i][j] != 0) {
board[i][j + 1] = board[i][j];
board[i][j] = 0;
} else if (board[i][j + 1] == board[i][j] && board[i][j] != 0) {
board[i][j + 1] = board[i][j + 1] + board[i][j];
board[i][j] = 0;
}
}
}
//checkLose();
}
After one swipe right, it should look like this:" ___,8,2 "(From the example before).

I did something similar to this in the past. I would to do it pretty much the same way as you are at the moment but add a Boolean array that checks if the tile has collided or not and only merges tiles that haven't been collided.
class Tile {
public int value;
public Boolean collided;
public Tile(int value) {
this.value = value;
collided = false;
}
public Tile attemptMerge(Tile target) {
if (target.value == value) {
Tile t = new Tile(value * 2);
t.collided = true;
return t;
} else {
return null;
}
}
public void reset() {
value = 0;
collided = false;
}
}
Somewhere in your main update loop:
void slideRight() {
for (int row = 0; row < 4; row++) {
for (int column = 3; column >= 0; column--) {
Tile current = board[row][column];
if (current.value == 0) continue;
for (int slot = column + 1; slot < 3; slot++) {
Tile target = board[row][slot];
if (target.value == 0) {
target.value = current.value;
current = target;
board[row][slot - 1].reset();
} else if (target.value == current.value) {
Tile product = target.merge(current);
if (!target.collided && !current.collided) {
current = product;
board[row][slot - 1].reset();
} else {
break;
}
} else {
break;
}
}
}
}
}
I believe something along those lines should work. Sorry if the logic is a bit flawed.

Java gomoku minimax

I'm trying to create a strategy that will play against human or another strategy for the game Gomoku. I already have some kind of minimax function, although i don't quite understand how does it work and i also have a getscore function, which should send back the best score to minimax ? But the problem is that my getScore function does not recognize if there are 4 or 5 circles in a row/col/diagonally.
Here is my code:
public class JarmoStrategyV1 implements ComputerStrategy {
public static int Lrow = 0;
public static int Lcol = 0;
public static int Drow = 0;
public static int Dcol = 0;
public static final int E = 0;
public static final int X = 1; // black
public static final int O = -1; // white
public static final int WINSCORE = 100;
private static final int WINCOUNT = 5;
public Location getMove(SimpleBoard board, int player) {
// let's operate on 2-d array
int[][] b = board.getBoard();
System.out.println(getScore(b, player));
for (int row = 0; row < b.length; row++) {
for (int col = 0; col < b[0].length; col++) {
if (b[row][col] == SimpleBoard.EMPTY) {
// first empty location
return new Location(row, col);
}
}
}
return null;
}
#Override
public String getName() {
return "Student name";
}
public static int minimax(int[][] board, int player, int depth) {
if (getScore(board, player) == WINSCORE) {
//
return WINSCORE;
}
if (depth == 2) {
return getScore(board, player);
}
int max = Integer.MIN_VALUE;
if (player == -1){
max = Integer.MAX_VALUE;
}
System.out.println(max);
List<Location> possibleMoves = getPossibleMoves(board);
for (Location loc : possibleMoves) {
board[loc.getRow()][loc.getColumn()] = player;
int newplayer = 0 - player;
if(newplayer == 1){
int value = minimax(board, newplayer,depth + 1);
if(value < max) {
max = value;
}
}
if (newplayer == -1){
int value = minimax(board, newplayer, depth + 1);
if (value > max) {
max = value;
}
}
board[loc.getRow()][loc.getColumn()] = E;
}
return max;
}
public static int getScore(int[][] board, int muutuja) {
//int yks = 0;
for (int row = 0; row < board.length; row++) {
for (int col = 0; col < board[row].length; col++) {
if (board[row][col] == muutuja) {
if (row <= (board.length - 5)) {
if (col <= board.length && getCount(board, row, col, 0, 1, muutuja, WINCOUNT) >= (WINCOUNT - 1) && getCount(board, row, (col + 4), 0, 1, E, 1 ) >= 1) return 1; // - 4 in a row
if (row >= 1 && getCount(board, row, col, 1, 0, muutuja, WINCOUNT) >= (WINCOUNT -1) && getCount(board, (row - 1), col, 1, 0, E, 1) == 1) return 1;
if (getCount(board, row, col, 1, 0, muutuja, WINCOUNT) >= WINCOUNT) return 100; // | 5 in a row
if (col <= WINCOUNT && getCount(board, row, col, 1, 1, muutuja, WINCOUNT) >= WINCOUNT) return 100; // \
if (col >= WINCOUNT && getCount(board, row, col, 1, -1, muutuja, WINCOUNT) >= WINCOUNT) return 100; // /
}
if (col <= WINCOUNT && getCount(board, row, col, 0, 1, muutuja, WINCOUNT) >= WINCOUNT) return 100; // -
}
}
}
return 0;
}
public static int getCount(int[][] board, int row, int col, int rowd, int cold, int player, int test) {
int count = 0;
for (int i = 0; i < test; i++) {
if (board[row + i * rowd][col + i * cold] == player) count++;
else break;
}
return count;
}
public static ArrayList<Location> getPossibleMoves(int[][] board) {
ArrayList<Location> availableMoves = new ArrayList<Location>();
for (int row = 0; row < board.length; row++) {
for (int col = 0; col < board[row].length; col++) {
if (board[row][col] == E) {
availableMoves.add(new Location(row, col));
}
}
}
return availableMoves;
}
}
There seems to be some kind of a problem with getScore, when i run this code then i can only play for a while until my Gomoku app crashes.
If you want to try this out yourself then you can open this via Eclipse.
Download the project file: http://www68.zippyshare.com/v/feWl2QwC/file.html
Import it to eclipse projects/workspace.
And you also have to build path to those 2 jar files in lib folder.
NOTE: I can only edit files in gomoku.strategies package.

the stacktrace shows an exception. add debug print or run with debugger
java.lang.IllegalArgumentException: It's computer's turn, pass the player to makeMove()
at gomoku.Game.makeMove(Game.java:476)

java:generalized 8 queen to work for any initial state using depth first search [duplicate]

i am try to implement 8 queen using depth search for any initial state it work fine for empty board(no queen on the board) ,but i need it to work for initial state if there is a solution,if there is no solution for this initial state it will print there is no solution
Here is my code:
public class depth {
public static void main(String[] args) {
//we create a board
int[][] board = new int[8][8];
board [0][0]=1;
board [1][1]=1;
board [2][2]=1;
board [3][3]=1;
board [4][4]=1;
board [5][5]=1;
board [6][6]=1;
board [7][7]=1;
eightQueen(8, board, 0, 0, false);
System.out.println("the solution as pair");
for(int i=0;i<board.length;i++){
for(int j=0;j<board.length;j++)
if(board[i][j]!=0)
System.out.println(" ("+i+" ,"+j +")");
}
System.out.println("the number of node stored in memory "+count1);
}
public static int count1=0;
public static void eightQueen(int N, int[][] board, int i, int j, boolean found) {
long startTime = System.nanoTime();//time start
if (!found) {
if (IsValid(board, i, j)) {//check if the position is valid
board[i][j] = 1;
System.out.println("[Queen added at (" + i + "," + j + ")");
count1++;
PrintBoard(board);
if (i == N - 1) {//check if its the last queen
found = true;
PrintBoard(board);
double endTime = System.nanoTime();//end the method time
double duration = (endTime - startTime)*Math.pow(10.0, -9.0);
System.out.print("total Time"+"= "+duration+"\n");
}
//call the next step
eightQueen(N, board, i + 1, 0, found);
} else {
//if the position is not valid & if reach the last row we backtracking
while (j >= N - 1) {
int[] a = Backmethod(board, i, j);
i = a[0];
j = a[1];
System.out.println("back at (" + i + "," + j + ")");
PrintBoard(board);
}
//we do the next call
eightQueen(N, board, i, j + 1, false);
}
}
}
public static int[] Backmethod(int[][] board, int i, int j) {
int[] a = new int[2];
for (int x = i; x >= 0; x--) {
for (int y = j; y >= 0; y--) {
//search for the last queen
if (board[x][y] != 0) {
//deletes the last queen and returns the position
board[x][y] = 0;
a[0] = x;
a[1] = y;
return a;
}
}
}
return a;
}
public static boolean IsValid(int[][] board, int i, int j) {
int x;
//check the queens in column
for (x = 0; x < board.length; x++) {
if (board[i][x] != 0) {
return false;
}
}
//check the queens in row
for (x = 0; x < board.length; x++) {
if (board[x][j] != 0) {
return false;
}
}
//check the queens in the diagonals
if (!SafeDiag(board, i, j)) {
return false;
}
return true;
}
public static boolean SafeDiag(int[][] board, int i, int j) {
int xx = i;
int yy = j;
while (yy >= 0 && xx >= 0 && xx < board.length && yy < board.length) {
if (board[xx][yy] != 0) {
return false;
}
yy++;
xx++;
}
xx = i;
yy = j;
while (yy >= 0 && xx >= 0 && xx < board.length && yy < board.length) {
if (board[xx][yy] != 0) {
return false;
}
yy--;
xx--;
}
xx = i;
yy = j;
while (yy >= 0 && xx >= 0 && xx < board.length && yy < board.length) {
if (board[xx][yy] != 0) {
return false;
}
yy--;
xx++;
}
xx = i;
yy = j;
while (yy >= 0 && xx >= 0 && xx < board.length && yy < board.length) {
if (board[xx][yy] != 0) {
return false;
}
yy++;
xx--;
}
return true;
}
public static void PrintBoard(int[][] board) {
System.out.print(" ");
for (int j = 0; j < board.length; j++) {
System.out.print(j);
}
System.out.print("\n");
for (int i = 0; i < board.length; i++) {
System.out.print(i);
for (int j = 0; j < board.length; j++) {
if (board[i][j] == 0) {
System.out.print(" ");
} else {
System.out.print("Q");
}
}
System.out.print("\n");
}
}
}
for example for this initial state it give me the following error:
Exception in thread "main" java.lang.StackOverflowError
i am stuck, i think the error is infinite call for the method how to solve this problem.
any idea will be helpful,thanks in advance.
note:the broad is two dimensional array,when i put (1) it means there queen at this point.
note2:
we i put the initial state as the following it work:
board [0][0]=1;
board [1][1]=1;
board [2][2]=1;
board [3][3]=1;
board [4][4]=1;
board [5][5]=1;
board [6][6]=1;
board [7][1]=1;

[EDIT: Added conditional output tip.]
To add to #StephenC's answer:
This is a heck of a complicated piece of code, especially if you're not experienced in programming Java.
I executed your code, and it outputs this over and over and over and over (and over)
back at (0,0)
01234567
0
1 Q
2 Q
3 Q
4 Q
5 Q
6 Q
7 Q
back at (0,0)
And then crashes with this
Exception in thread "main" java.lang.StackOverflowError
at java.nio.Buffer.<init>(Unknown Source)
...
at java.io.PrintStream.print(Unknown Source)
at java.io.PrintStream.println(Unknown Source)
at Depth.eightQueen(Depth.java:56)
at Depth.eightQueen(Depth.java:60)
at Depth.eightQueen(Depth.java:60)
at Depth.eightQueen(Depth.java:60)
at Depth.eightQueen(Depth.java:60)
...
My first instinct is always to add some System.out.println(...)s to figure out where stuff is going wrong, but that won't work here.
The only two options I see are to
Get familiar with a debugger and use it to step through and analyze why it's never stopping the loop
Break it down man! How can you hope to deal with a massive problem like this without breaking it into digestible chunks???
Not to mention that the concept of 8-queens is complicated to begin with.
One further thought:
System.out.println()s are not useful as currently implemented, because there's infinite output. A debugger is the better solution here, but another option is to somehow limit your output. For example, create a counter at the top
private static final int iITERATIONS = 0;
and instead of
System.out.println("[ANUMBERFORTRACING]: ... USEFUL INFORMATION ...")
use
conditionalSDO((iITERATIONS < 5), "[ANUMBERFORTRACING]: ... USEFUL INFORMATION");
Here is the function:
private static final void conditionalSDO(boolean b_condition, String s_message) {
if(b_condition) {
System.out.println(s_message);
}
}
Another alternative is to not limit the output, but to write it to a file.
I hope this information helps you.
(Note: I edited the OP's code to be compilable.)

You asked for ideas on how to solve it (as distinct from solutions!) so, here's a couple of hints:
Hint #1:
If you get a StackOverflowError in a recursive program it can mean one of two things:
your problem is too "deep", OR
you've got a bug in your code that is causing it to recurse infinitely.
In this case, the depth of the problem is small (8), so this must be a recursion bug.
Hint #2:
If you examine the stack trace, you will see the method names and line numbers for each of the calls in the stack. This ... and some thought ... should help you figure out the pattern of recursion in your code (as implemented!).
Hint #3:
Use a debugger Luke ...
Hint #4:
If you want other people to read your code, pay more attention to style. Your indentation is messed up in the most important method, and you have committed the (IMO) unforgivable sin of ignoring the Java style rules for identifiers. A method name MUST start with a lowercase letter, and a class name MUST start with an uppercase letter.
(I stopped reading your code very quickly ... on principle.)

Try to alter your method IsValid in the lines where for (x = 0; x < board.length - 1; x++).
public static boolean IsValid(int[][] board, int i, int j) {
int x;
//check the queens in column
for (x = 0; x < board.length - 1; x++) {
if (board[i][x] != 0) {
return false;
}
}
//check the queens in row
for (x = 0; x < board.length - 1; x++) {
if (board[x][j] != 0) {
return false;
}
}
//check the queens in the diagonals
if (!SafeDiag(board, i, j)) {
return false;
}
return true;
}

Sudoku algorithm with backtracking does not return any solution

i'm a bit stuck with the Sudoku algorithm, i coded it using backtrack, and following the theorical steps this should work, and i tried to debuge it, but is too hard (and yes, it solve some numbers and does things)
i paste the code, i hope that you can help me, i really can't see where the problem is...
public void backtracking(int row,int col){
if(row > 8){
System.out.println("Solution Found!!");
printSudoku();
}
if (m[row][col] != 0){
next(row, col);
}
else {
for(int i =1; i < n;i++)
if(row(row, i) && col(col, i)) {
m[row][col] =i;
next(row, col);
}
m[row][col] = 0;
}
}
public void next( int row, int col ) {
if( col < 8)
backtracking( row, col + 1 ) ;
else
backtracking( row+ 1, 0 ) ;
}
public boolean region(int x, int y, int numReg) {
x = (x / 3) * 3 ;
y = (y / 3) * 3 ;
for( int r = 0; r < 3; r++ )
for( int c = 0; c < 3; c++ )
if( m[x+r][y+c] == numReg )
return false ;
return true ;
}
public boolean row(int x, int k){
for(int i =0; i < 9; i++)
if(m[x][i] == k)
return false;
return true;
}
public boolean col(int x, int k){
for(int i =0; i < 9; i++)
if(m[i][x] == k)
return false;
return true;
}
I ommited the "printSudoku" method, is just a double for and you know.

The code seems almost right.
As far as i can see you just forgot to call the region method. And I can't see where the variable n is coming from.
Try it with this slightly modified backtracking method:
public static void backtracking(int row, int col) {
if (row > 8) {
System.out.println("Solution Found!!");
printSudoku();
System.exit(0); //exiting after solution is found
}
if (m[row][col] != 0) {
next(row, col);
} else {
for (int i = 1; i <= 9; i++) //replaced i < n with i<=9
if (row(row, i) && col(col, i) && region(row, col, i)) { //calling region method too
m[row][col] = i;
next(row, col);
}
m[row][col] = 0;
}
}