I'm coding a Sudoku solver and my teacher recommended that I use a 3d array and since I've never used 3d arrays; I'm having trouble figuring out how to create a loop to iterate through the rows and one through the columns. How would you go about doing this?
Edit: I figured out how to iterate through every third column/row and hopefully I should be able to do the other six eventually, but am I heading in the right direction?
int[][][] = board[9][3][3];
public boolean columnCheck(int[][][] board)
{
boolean filled = false;
for(int i = 0; i < board.length; i++)
{
for(int j = 0; j < board[0].length; j++)
{
System.out.println(board[i][j][0]);
}
}
return true;
}
public boolean rowCheck(int[][][] board)
{
boolean filled = false;
for(int i = 0; i < board.length; i++)
{
for(int j = 0; j < board[0].length; j++)
{
System.out.println(board[i][0][j]);
}
}
return true;
You can use 3 for loops to iterate through a 3D array, e.g.:
public static void main(String[] args) throws FileNotFoundException {
int[][][] array = new int[9][3][3];
for(int i=0 ; i<array.length ; i++){
for(int j=0 ; j<array[i].length ; j++){
for(int k=0 ; k<array[i][j].length ; k++){
System.out.println("[" + i + "][" + j + "][" + k + "]:" + array[i][j][k]);
}
}
}
}
However, for sudoku game, you don't need a 3D array. 2D array would suffice.
public class Main {
public static void main(String[] args) {
int[][][] board = new int[3][3][9];
// Assume that first parameter is row
// The second is column
// Iterating through first row (board[0])
for (int i = 0; i < 3; i++) {
// i is col number
for (int j = 0; j < 9; j++) {
//j is block number
System.out.println(board[0][i][j]);
}
}
// Iterating through second column
for (int i = 0; i < 3; i++) {
// i is row number
for (int j = 0; j < 9; j++) {
// j is block number
System.out.println(board[i][1][j]);
}
}
}
}
I suppose that your 3d array represents the sudoku as follows:
The '9' stands for the 9 small 3x3 blocks. The first '3' for each row of the block and the second '3' for the columns of each block.
That would give the following:
array[0][x][y] | array[1][x][y] | array[2][x][y]
----------------------------------------------------
array[3][x][y] | array[4][x][y] | array[5][x][y]
----------------------------------------------------
array[6][x][y] | array[7][x][y] | array[8][x][y]
To iterate over each row you can do the following:
// The first three rows
// You can probably figure out yourself how to do the last 6,
// and how to combine those 3 seperate sections
for (int i=0; i<3; i++) {
for (int j=0; j<3; j++) {
for (int k=0; j<3; k++) {
System.out.println(array[j][i][k]);
}
}
}
// The first three columns
for (int i=0; i<3; i++) {
for (int j=0; j<7; j+=3) {
for (int k=0; k<3; k++) {
System.out.println(array[j][k][i]);
}
}
}
I hope this will get you going, without solving it all for you.
Related
So I'm currently playing around with multidimensional arrays (2D) and I'm trying to reverse the order of each array in a 2-d array.
So I have a 2D-array set as:
int firstArray[][] = {{5,6,7,8,9,10}, {11,12,13,14,15,16}}
I have manually looked through the issue to see where I may have went wrong, to see which part of my code would end up going out of bounds in regards to my for-loops. The -1 part also caught me off guard.
I have began doing reverses on a regular 1-d array, and tried to apply the same concept to multidimensional arrays.
class Test2 {
public static void main (String[] args) {
int firstArray[][] = {{5,6,7,8,9,10}, {10,11, 12, 13, 14, 15}};
System.out.println("FIRST ARRAY");
display(firstArray);
}
public void display(int [][]num) {
for (int i = 0; i < num.length; i++) {
for (int j = 0; j < num[i].length/2; j++) {
int temp = num[i][j];
num[i][j] = num[i][num.length-1-j];
num[i][num.length-1-j] = temp;
}
}
for (int a = 0; a < num.length; a++) {
for (int b = 0; b < num[a].length; b++) {
System.out.print(num[a][b] + "\t");
}
System.out.println();
}
}
}
I want the output using my display method to basically be a reverse of the arrays in my 2-d array:
10 9 8 7 6 5
15 14 13 12 11 10
The issue that I'm getting is an
Exception in thread "main"java.lang.ArrayIndexOutOfBoundsException: -1
ArrayIndexOutOfBoundsException: -1
at Test2.display(Test2.java:30)
at Test2.main(Test2.java:20)
You are using the length of the wrong dimension.
With num.length you are using the number of rows and not the number of columns of the current row.
You need to change that to num[i].length.
public static void display(int [][]num) {
for (int i = 0; i < num.length; i++) {
for (int j = 0; j < num[i].length/2; j++) {
int temp = num[i][j];
num[i][j] = num[i][num[i].length-1-j];
num[i][num[i].length-1-j] = temp;
}
}
for (int a = 0; a < num.length; a++) {
for (int b = 0; b < num[a].length; b++) {
System.out.print(num[a][b] + "\t");
}
System.out.println();
}
}
Notice you wrote num[i][num.length-1-j];
num.length-1-j is basically 2 - 1 -j.
public static void display(int [][]num) {
for (int i = 0; i < num.length; i++) {
for (int j = 0; j < num[i].length/2 ; j++) {
int temp = num[i][j];
num[i][j] = num[i][num[i].length-1-j];
num[i][num[i].length-1-j] = temp;
}
}
for (int a = 0; a < num.length; a++) {
for (int b = 0; b < num[a].length; b++) {
System.out.print(num[a][b] + "\t");
}
System.out.println();
}
}
How can I find the total sum for each two dimensional array row? I'm completely stuck...
public static void main(String[] args) {
int [][] grid = new int [10][10];
for (int i = 0; i < grid.length; i++) {
for (int j = 0; j < grid[i].length; j++) {
grid[i][j] = (int)(Math.random()*99);
}
}
for(int i = 0; i < 10; i++) {
for(int j = 0; j < 10; j++) {
System.out.print("1.");
System.out.printf("%5d ", grid[i][j]);
}
System.out.println();
}
}
My current output is:
How can I show the total sum for each row in the end of the row and show column numbers
For the sum of a row, this should do. In a similar way within the i loop, if you need to count the column as well;
for(int i = 0; i < 10; i++) {
int jSum = 0;
for(int j = 0; j < 10; j++) {
jSum += grid[i][j];
System.out.print("1.");
System.out.printf("%5d ", grid[i][j]);
}
System.out.printf(" %5d", jSum);
System.out.println();
}
On the column numbering:
Either you just pust put a static print in the beginning (like print "1 2 3 4..."), or you put the following with the j loop:
if (i == 0) System.out.printf("%5d ", j); // only prints in first loop / row - print 1,2,3,4,5....
I have to print the following numbers using nested loops, and I kinda have an idea how, but not how to execute it.
000111222333444555666777888999
000111222333444555666777888999
000111222333444555666777888999
My code so far is something like:
public class opgave_2 {
public static void main(String[] args) {
final int first = 3;
final int second = 3;
final int third = 9;
for (int i = 0; i <= first ; i++) {
for (int j = i; j <= second; j++) {
for (int k = j; k <= third; k++) {
System.out.print(i);
}
}
}
}
}
You should proceed by steps to resolve such problem.
First, you want to print a number 3 times :
int myNumber = 0;
for(int i=0; i<3; i++) {
System.out.print(myNumber);
}
Second, you want to repeat it 9 times and your number to vary from 0 to 9 (seems like an index of loop) :
for(int myNumber=0; myNumber<=9; myNumber++) {
for(int i=0; i<3; i++) {
System.out.print(myNumber);
}
}
Third, you want to display this line 3 times :
for(intj=0; j<3; j++) {
for(int myNumber=0; myNumber<=9; myNumber++) {
for(int i=0; i<3; i++) {
System.out.print(myNumber);
}
}
System.out.println(""); //new line
}
What about something like this:
for (int i = 0; i < 3; i++) {
for (int j = 0; j <= 9; j++) {
System.out.printf("%1$s%1$s%1$s", j);
}
System.out.println();
}
Which uses 2 nested loops. The first to print the line 3 times, and the second to print the numbers per line
you can use a loop, that loops 3 times. in that you put a loop that prints every number from 0 to 9 3 times in a row within the same line
for(int a = 0; a < 3; a++){
for(int i = 0; i < 10; i++){
System.out.print(i+""+i+""+i);
}
System.out.println(); //for the new line
}
or
for(int a = 0; a < 3; a++){
for(int i = 0; i < 10; i++){
System.out.print(i);
System.out.print(i);
System.out.print(i);
}
System.out.println(); //for the new line
}
this should do
This is my current code:
public static void main(String[] args) {
int [][] twoD = new int [5][5];
/*for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
System.out.print(twoD[i][j] + "");
}
}*/
}
}
I can't seem to do it. I got confused and I removed the part of testing w/commenting. Just ignore that.
I am aiming to get a two dimensional array like this:
1 2 3 4 5
2 4 6 8 10
3 6 9 12 15
4 8 12 16 20
5 10 15 20 25
However, I just don't get it. How can I get that result? I'm a beginner at java.
First, you need to populate the array with data, and you forgot System.out.println for each row of the array.
int [][] twoD = new int [5][5];
// populate array with data
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
twoD[i][j] = (j+1)*(i+1);
}
}
// print result
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
System.out.print(twoD[i][j]);
System.out.print(" ");
}
System.out.println();
}
You have to populate the data as well:
int[][] arr = new int [5][5];
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
arr[i][j] = (j+1)*(i+1);
}
}
And the code to print would be:
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
System.out.print(arr[i][j] + " ");
}
System.out.println();
}
You are doing fine, you just need to put line jump System.out.println(); every time the second for ends
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
System.out.print(twoD[i][j] + " ");
}
System.out.println();
}
You are on the right track, that for loop will print out the array like that, all you need to do is print a new line character after finishing the for(j) loop. But, at least in the snippet you posted, you aren't actually doing any assignments, so there aren't any values in your array to print, Java will initialize all ints to zero for you.
The array doesn't just automatically populate with incrementing integers, rather each cell of the array will automatically initialized to 0, you have to set the values you want the array to contain. You can use the concept of your testing class to do this if you wish, just set each cell of the 2D array to a certain value. After that, you can print out the array, making sure to print a each row of the array on a new line. For instance:
public static void main(String[] args) {
int [][] twoD = new int [5][5];
int increment = 1;
for(int i = 0; i<5; i++){
for(int j = 0; j<5; j++){
twoD[i][j] = increment++;
}
}
for(i = 0; i<5; i++){
for(j = 0; j<5; j++){
System.out.print(twoD[i][j] + " ");
}
System.out.println();
}
}
The first set of nested for loops will set each of the cells of the 2D array to the incremented integers you want (note increment++ will first set the cell to the value increment currently is, then add one to the variable). The second set of nested for loops will print out the array as you desire.
refer this code
int[][] twoD = new int[5][5];
// add values to array
for (int i = 0; i < 5; i++) {
int val = 1;
val = val + i;
for (int j = 0; j < 5; j++) {
twoD[i][j] = val * (j + 1);;
}
}
// Print array
for (int i = 0; i < 5; i++) {
for (int j = 0; j < 5; j++) {
System.out.print(twoD[i][j] + " ");
}
System.out.println();
}
as others pointed out you need to print it nicely to see the pattern, i and j are indices of your array. However, I see that you have a nice pattern so just running two loops won't solve the problem.
Maybe something like this would help (not giving exact answer intentionally)
int [][] twoD = new int [5][5];
int i;
// initialize
int c = 1; int j = 0;
for(c=1; c<5; c++) {
for( i = 1; i<=5; i++){
twoD[i-1][c-1] = c*c*i; twoD[c-1][i-1]=c*c*i;
}
}
for( i = 0; i<5; i++) {
for( j = 0; j<5; j++) {
System.out.print(twoD[i][j]);System.out.print(" " );
}
System.out.println("\n");
}
I'm looking for a way to add up the elements of the rows of an array and get that sum. I have to get the column's sum as well.
The array looks something like this:
{{45.24, 54.67, 32.55, 25.61},
{65.29, 49.75, 32.08, 26.11},
{25.24, 54.33, 34.55, 28.16}};
For example, I would add 45.24, 65.29, and 25.24 to get the sum of that part of the columns. I would then have to add the other 3 columns up as well.
Same goes for the rows.
I keep getting errors concerning the variable types. Is there a way to do this? Thanks.
The logic Would be --->
for(i = 0; i < columns; i++)
{
for(j=0; j<rows; j++)
{
sum+=arr[j][i];
}
}
Opposite for Columns
I think you should define the type of numbers your array will handle, if I use float numbers I can have some code like the class bellow to do the type of operations you are asked for. You can also add some decimal formatting.
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
float myarray[][]= {
{45.24f, 54.67f, 32.55f, 25.61f},
{65.29f, 49.75f, 32.08f, 26.11f},
{25.24f, 54.33f, 34.55f, 28.16f}
};
float row[] = new float[3];
float column[] = new float[4];
for (int i=0; i < 3; i++) {
float rowvalue = 0f;
for (int j=0; j < 4; j++) {
System.out.print(myarray[i][j]+" ");
rowvalue+=myarray[i][j];
}
row[i]=rowvalue;
System.out.println("");
}
System.out.println("");
for (int i=0; i < 4; i++) {
float colvalue = 0f;
for (int j=0; j < 3; j++) {
System.out.print(myarray[j][i]+" ");
colvalue+=myarray[j][i];
}
column[i]=colvalue;
System.out.println("");
}
System.out.println("Rows answer:");
for (int i=0; i < 3; i++) {
System.out.println(row[i]);
}
System.out.println("Columns answer:");
for (int i=0; i < 4; i++) {
System.out.println(column[i]);
}
}
}
Suppose you have nxn matrix. The idea is to identify the pattern.
Row values
i j
0 0
0 1
0 2
Column values
i j
0 0
1 0
2 0
The position of i and j values is reversed.
Let's assume we have an array a[][]. The logic would be:
for (int i=0; i<n; i++) {
int row = 0, col = 0;
for (int j=0; j<n; j++) {
row += a[i][j];
col += a[j][i];
}
System.out.println("row" + i + " = " + row);
System.out.println("col" + i + " = " + col);
}
I assumed you wanted the sum of each row and column separately. You can modify it accordingly.