用Java旋转指定的4x4列数组

Question

Basically, I have a 4x4 array with integers 0-15 initialised in it. This little task is to rotate the given column of the array so for example if the array is :

  14   0   1  12
  13   4   2   3
   7   6  11   8
   5  15   9  10

After application of rotateColumn(3), the array should look as follows:

      14   0   1  10
      13   4   2  12
       7   6  11   3
       5  15   9   8

I have managed to implement the row rotation method and the code is:

public static void rotateRow(int[][] arr, int row) {
        int newCurrent = arr[row][arr.length - 1];
        int nextCurrent;
        for (int currentIndex = 0; currentIndex < arr.length; currentIndex++) { 
            nextCurrent = arr[row][currentIndex];
            arr[row][currentIndex] = newCurrent;
            newCurrent = nextCurrent;
        }
    }

I tried a similar code for the column method but it didn't work out:

public static void rotateColumn(int[][] arr, int column) {
    int newCurrent1 = arr[column][arr.length - 1];
    int nextCurrent1 ;
    for (int currentIndex1 = 0; currentIndex1 < arr.length; currentIndex1++){
        nextCurrent1 = arr[column][currentIndex1];
        arr[column][currentIndex1] = newCurrent1;
        newCurrent1 = nextCurrent1;
    }

    }

The whole code for the Program is:

public class Puzzle {

    public static final int N = 4;
    public static final int NUMBER_OF_ROTATIONS = 5;

    public static void main(String[] args) {
        int[][] puzzle = new int[N][N];
        reset(puzzle);
        test(puzzle);
        reset(puzzle);
        scramble(puzzle);
        System.out.println("### Testing puzzle game play\n");
        play(puzzle);
    }

    public static void print(int[][] puzzle) {
        for (int[] row : puzzle) {
            for (int elem : row) {
                System.out.printf("%4d", elem);
            }
            System.out.println();
        }
        System.out.println();
    }

    public static void test(int[][] puzzle) {
        System.out.println("### Testing reset method\n");
        print(puzzle);
        System.out.println("### Testing rotate methods\n");
        print(puzzle);
        for (int i = 0; i < N; i++) {
            System.out.println("### rotateColumn(" + i + ")\n");
            rotateColumn(puzzle, i);
            print(puzzle);
            System.out.println("### rotateRow(" + i + ")\n");
            rotateRow(puzzle, i);
            print(puzzle);
        }
        reset(puzzle); 
        System.out.println("### Testing random rotations\n");
        print(puzzle); 
        for (int i = 0; i < 5; i++){
            randomRotation(puzzle);
            print(puzzle); 
        }
    }

    public static void reset(int[][] puzzle) {
        for (int i = 0; i < N; i++) {
            for (int j = 0; j < N; j++)
                puzzle[i][j] = i * N + j;
        }
    }

    public static void scramble(int[][] puzzle) {
        for (int i = 0; i < NUMBER_OF_ROTATIONS; i++) {
            randomRotation(puzzle);
        }
    }




    public static void rotateRow(int[][] arr, int row) {
        int newCurrent = arr[row][arr.length - 1];
        int nextCurrent;
        for (int currentIndex = 0; currentIndex < arr.length; currentIndex++) { 
            nextCurrent = arr[row][currentIndex];
            arr[row][currentIndex] = newCurrent;
            newCurrent = nextCurrent;
        }
    }





    // TODO: Implement method as specified in assignment brief 

    public static void rotateColumn(int[][] arr, int column) {
    int newCurrent1 = arr[column][arr.length - 1];
    int nextCurrent1 ;
    for (int currentIndex1 = 0; currentIndex1 < arr.length; currentIndex1++){
        nextCurrent1 = arr[column][currentIndex1];
        arr[column][currentIndex1] = newCurrent1;
        newCurrent1 = nextCurrent1;
    }

    }


    // TODO: Implement method as specified in assignment brief 

    public static void randomRotation(int[][] puzzle) {
    }

    // TODO: Implement method as specified in assignment brief 

    static void play(int[][] puzzle) {
    }

}

Could someone point out what I need to do right to make sure it works properly? Than you very much :).

Answer 1

It seems you are confusing the memory layout of rows and columns. The data array is always an array of rows. So you need to change how to address individual elements. You need minor tweaking on your original method. The following untested code derived from rotateRow() should make the difference.

    public static void rotateColumn(int[][] arr, int col) {
        int newCurrent = arr[arr.length - 1][col];
        int nextCurrent;
        for (int currentIndex = 0; currentIndex < arr.length; currentIndex++) { 
            nextCurrent = arr[currentIndex][col];
            arr[currentIndex][col] = newCurrent;
            newCurrent = nextCurrent;
        }
    }

Answer 2

How about this?

public void rotateColumn(int[][] arr, int column) {
    int[] col = new int[arr.length];
    for(int row=0; row<arr.length; row++) {
        col[row] = arr[row][column];
    }
    for(int row=0; row<arr.length; row++) {
        arr[row][column] = col[(row==0) ? arr.length-1 : row-1];
    }
}