切換二維數組的列

Question

所以我的問題是我無法像在單個變量數組中那樣能夠切換2d數組的元素。 而不是切換元素，而只是不斷地對其進行重寫...

for (int column = 0; column < m[0].length; column++) {
    shufcol = (int)(Math.random()*4);
    temp = column;
    System.out.println(shufcol);

    for(int row = 0; row < m.length; row++) {
        temp = row;
        m[row][temp]=m[row][column];
        m[row][column]= m[row][shufcol];
        m[row][temp] = m[row][shufcol];
    }
}

輸入數組（3X4）{{0 1 2 3} {1 4 5 6} {0 7 8 9}}

輸出數組{{2 2 3 2} {5 5 6 5} {8 8 9 8}}

如果您對math.random感到好奇，那只是生成一個0到3之間的隨機列進行切換。 同樣，問題在於為什么它只重寫元素而不切換元素？

Answer 1

我不完全了解您最終想要實現的目標（因為您還沒有告知），但是我認為，如果您重新閱讀這段代碼：

temp = row;
m[row][temp]=m[row][column];
m[row][column]= m[row][shufcol];
m[row][temp] = m[row][shufcol];

幾次嘗試用紙和筆執行它，您會發現錯誤。

Answer 2

這將在其行內切換元素：

    //input array (3X4) {{0 1 2 3} {1 4 5 6} {0 7 8 9}}
    int[][] m = {{0, 1, 2, 3}, {1, 4, 5, 6}, {0, 7, 8, 9}};


    for (int column = 0; column < m[0].length; column++) {
        int shufcol = (int)(Math.random()*4);
        int shufrow = (int)(Math.random()*3); //need row to switch with, too
        for(int row = 0; row < m.length; row++) {
            if(row == shufrow){
                int tempField =m[row][column];
                m[row][column]= m[row][shufcol];
                m[row][shufcol] = tempField;
                System.out.println("In row " + row + " : column " + column + " was switched with column " + shufcol + "!");
                break; //just switch once per row, easier debugging ^^-d
            }
        }
    }

    //print output array
    for(int row = 0; row < m.length; row++) {
        String line = "\n";
        for (int column = 0; column < m[0].length; column++) {
            line += m[row][column] + " ";
        }
        System.out.print(line);
    }

輸出：

In row 2 : column 0 was switched with column 2!
In row 0 : column 1 was switched with column 2!
In row 1 : column 2 was switched with column 3!
In row 0 : column 3 was switched with column 2!

0 2 3 1 
1 4 6 5 
8 7 0 9 

由於我不確定您要做什么，因此這里是隨機切換整個數組中的元素：

    //input array (3X4) {{0 1 2 3} {1 4 5 6} {0 7 8 9}}
    int[][] m = {{0, 1, 2, 3}, {1, 4, 5, 6}, {0, 7, 8, 9}};

    for (int column = 0; column < m[0].length; column++) {
        int shufcol = (int)(Math.random()*4);
        int shufrow = (int)(Math.random()*3); //need row to switch with, too
        //there is no point in duplicating the count variable of a loop!
        System.out.println(shufcol);

        for(int row = 0; row < m.length; row++) {
            //check that random field is not current field!
            if(row != shufrow && column != shufcol){
                //switch current with random
                int temp = m[row][column]; // le backuppe
                m[row][column] = m[shufrow][shufcol]; // write le new value of "random source field" to current field
                m[shufrow][shufcol] = temp; // write value of current field to "random source field"
                System.out.println("switched [" + row + "][" + column + "] with [" + shufrow + "]["+ shufcol + "]");
                break; // use break to switch only once per row, easier debugging ^^-d
            }
            else {
                System.out.println("will not switch with self!");
            }

        }
    }

    //print output array
    for(int row = 0; row < m.length; row++) {
        String line = "\n";
        for (int column = 0; column < m[0].length; column++) {
            line += m[row][column] + " ";
        }
        System.out.print(line);
    }

產生以下輸出：

2
switched [0][0] with [2][2]
0
switched [0][1] with [1][0]
0
switched [0][2] with [2][0]
2
switched [0][3] with [1][2]

8 1 0 5 
1 4 3 6 
2 7 0 9 

希望這可以幫助！ ^^-d

Answer 3

據我了解，這將切換所有行的列和shufcol中的值（我沒有對其進行測試）：

for (int column = 0; column < m[0].length; column++) {
    shufcol = (int)(Math.random()*4);
    System.out.println(shufcol);

    for(int row = 0; row < m.length; row++) {
        temp = m[row][shufcol];
        m[row][shufcol] = m[row][column];
        m[row][column] = temp;
    }
}