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I'm trying to write a code the takes two dimensional array "Sudoku" and arrange them into blocks

I'm trying to write a code the takes two dimensional array "Sudoku" (matrix.length * matrix.length) and I should check if the matrix is (n^2 * n^2) and a number (n) and I should arrange the rows into blocks (n * n). Any suggestions? if any body can do it if 4 "fors" i will be more than happy

public static int[][] blocks(int[][] matrix, int sqrtN) {
    int [][] returnedMatrix = new int [matrix.length][matrix.length];
    if (matrix.length !=  Math.pow(sqrtN, 2))
            throw new RuntimeException("Matrix length is not" + Math.pow(sqrtN, 2 ));
    for(int i=0 ; i <= matrix.length ;i=i+sqrtN) {
        for(int j=sqrtN; j <= matrix.length;j=j+1) {
            int temporarily = 

        }
    }
    return returnedMatrix;
}

for exsample

int[][] matrix1 = {{11,12,13,14},
{15,16,17,18},
{19,20,21,22},

{23,24,25,26}} ;

int[][] matBlocks1 = blocks (matrix1, 2) ;
/*
* matBlocks1 = {{11, 12, 15, 16},
* {13, 14, 17, 18},
* {19, 20, 23, 24},
* {21, 22, 25, 26}}
*/
Solution

  • The formulas you're looking for are:

    int r = (i/sqrtN)*sqrtN+j/sqrtN;
int c = (i%sqrtN)*sqrtN+j%sqrtN;
returnedMatrix[i][j] = matrix[r][c];

    Full code with tests:

    public static int[][] blocks(int[][] matrix, int sqrtN) {
    int n = matrix.length;
    if (n != Math.pow(sqrtN, 2))
        throw new RuntimeException("Matrix length is not" + Math.pow(sqrtN, 2));
    int[][] returnedMatrix = new int[n][n];
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            int r = (i/sqrtN)*sqrtN+j/sqrtN;
            int c = (i%sqrtN)*sqrtN+j%sqrtN;
            returnedMatrix[i][j] = matrix[r][c];
        }
    }
    return returnedMatrix;
}

public static void print(int[][] matrix) {
    for (int i = 0; i < matrix.length; i++) {
        for (int j = 0; j < matrix[i].length; j++) {
            System.out.print(matrix[i][j] + " ");
        }
        System.out.println();
    }
    System.out.println();
}

public static void main(String args[]) {
    int[][] matrix4 = {
        {1,1,2,2},
        {1,1,2,2},
        {3,3,4,4},
        {3,3,4,4}
    };
    print(blocks(matrix4, 2));

    int[][] matrix9 = {
        {1,1,1,2,2,2,3,3,3},
        {1,1,1,2,2,2,3,3,3},
        {1,1,1,2,2,2,3,3,3},
        {4,4,4,5,5,5,6,6,6},
        {4,4,4,5,5,5,6,6,6},
        {4,4,4,5,5,5,6,6,6},
        {7,7,7,8,8,8,9,9,9},
        {7,7,7,8,8,8,9,9,9},
        {7,7,7,8,8,8,9,9,9}
    };
    print(blocks(matrix9, 3));
}

    Output:

    1 1 1 1 
2 2 2 2 
3 3 3 3 
4 4 4 4 

1 1 1 1 1 1 1 1 1 
2 2 2 2 2 2 2 2 2 
3 3 3 3 3 3 3 3 3 
4 4 4 4 4 4 4 4 4 
5 5 5 5 5 5 5 5 5 
6 6 6 6 6 6 6 6 6 
7 7 7 7 7 7 7 7 7 
8 8 8 8 8 8 8 8 8 
9 9 9 9 9 9 9 9 9