Java 矩阵原地旋转

Question

我正在尝试用 Java 创建一个程序，该程序采用 NxN 矩阵并将其旋转到位。我正在实现一种方法，该方法将每一列更改为行来执行此操作。我的堆栈是正确的，我的循环也是正确的，因为我已输出它们进行检查。

Stack<Integer> takeCol = new Stack();

for (int i = 0; i < matrix.length; i++) {

    //take columns and make them rows (ROTATION METHOD)
    for (int j = matrix[i].length - 1; j >= 0; j--) {

        takeCol.push(matrix[j][i]);
    }

    //reverse stack
    Stack<Integer> temp = new Stack();
    while (!takeCol.isEmpty()) {

        temp.push(takeCol.pop());
    }

    //rotate matrix
    for (int j = 0; j < matrix[i].length; j++) {

        matrix[i][j] = temp.pop();
    }
}

我的临时堆栈是正确的，放置的 i 和 j 也是正确的。但是，这里是一个示例输出:

旋转之前:

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

旋转后:

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

完整代码:

公开课 Q1_7{

public static void createMatrix(int matrix[][]) {

    for (int i = 0; i < matrix.length; i++) {

        for (int j = 0; j < matrix[i].length; j++) {

            matrix[i][j] = (int)Math.round(Math.random() * 8) + 1;
        }
    }
}

public static void displayMatrix(int matrix[][]) {

    System.out.println("\n\n");

    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("\n\n");
}

public static void rotateMatrix(int matrix[][]) {

    Stack<Integer> takeCol = new Stack();

    for (int i = 0; i < matrix.length; i++) {

        //take columns and make them rows (ROTATION METHOD)
        for (int j = matrix[i].length - 1; j >= 0; j--) {

            takeCol.push(matrix[j][i]);
        }

        //reverse stack
        Stack<Integer> temp = new Stack();
        while (!takeCol.isEmpty()) {

            temp.push(takeCol.pop());
        }

        //rotate matrix
        for (int j = 0; j < matrix[i].length; j++) {

            matrix[i][j] = temp.pop();
        }
    }
    displayMatrix(matrix);
}

public static void main(String args[]) {

    Scanner s = new Scanner(System.in);

    System.out.println("Enter size of matrix to be rotated");
        int matrixSize = s.nextInt();
    //create matrix size of user input
    int matrix[][] = new int [matrixSize][matrixSize];

    createMatrix(matrix);
    displayMatrix(matrix);
    rotateMatrix(matrix);
    s.close();
}

}

Answer 1

好吧，下面的答案相当冗长 - 我已将调试日志添加到您的程序中，以便更轻松地跟踪正在发生的事情。问题是，代码在旋转之前覆盖值，因此例如。 9 在被读取之前被 4 覆盖。请参阅下面的代码和日志。 (另请注意，添加日志有助于调试)

输出为:

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


pushing num=[1] val=4
pushing num=[2] val=4
pushing num=[3] val=5
pushing num=[4] val=3
pushing temp num=[1] val=3
pushing temp num=[2] val=5
pushing temp num=[3] val=4
pushing temp num=[4] val=4
writing to m[0,0] val=4
writing to m[0,1] val=4    <-------- here: 9 is overridden by 4
writing to m[0,2] val=5
writing to m[0,3] val=3
pushing num=[5] val=1
pushing num=[6] val=7
pushing num=[7] val=5
pushing num=[8] val=4      <<----- here: we want 9 but is has been overridden 
pushing temp num=[5] val=4
pushing temp num=[6] val=5
pushing temp num=[7] val=7
pushing temp num=[8] val=1
writing to m[1,0] val=1
writing to m[1,1] val=7
writing to m[1,2] val=5
writing to m[1,3] val=4
pushing num=[9] val=8
pushing num=[10] val=6
pushing num=[11] val=5
pushing num=[12] val=5
pushing temp num=[9] val=5
pushing temp num=[10] val=5
pushing temp num=[11] val=6
pushing temp num=[12] val=8
writing to m[2,0] val=8
writing to m[2,1] val=6
writing to m[2,2] val=5
writing to m[2,3] val=5
pushing num=[13] val=2
pushing num=[14] val=5
pushing num=[15] val=4
pushing num=[16] val=3
pushing temp num=[13] val=3
pushing temp num=[14] val=4
pushing temp num=[15] val=5
pushing temp num=[16] val=2
writing to m[3,0] val=2
writing to m[3,1] val=5
writing to m[3,2] val=4
writing to m[3,3] val=3
4 4 5 3 
1 7 5 4 
8 6 5 5 
2 5 4 3 

代码是:

package sample;

import java.util.Stack;

public class A {

    void go(int[][] matrix) {

        Stack<Integer> takeCol = new Stack<>();

        int numPushTake=0;
        int numPushTemp=0;

        for (int i = 0; i < matrix.length; i++) {

            //take columns and make them rows (ROTATION METHOD)
            for (int j = matrix[i].length - 1; j >= 0; j--) {

                int val = matrix[j][i];
                System.out.printf("pushing num=[%d] val=%d%n", ++numPushTake, val);
                takeCol.push(val);
            }

            //reverse stack
            Stack<Integer> temp = new Stack();
            while (!takeCol.isEmpty()) {

                int val = takeCol.pop();
                System.out.printf("pushing temp num=[%d] val=%d%n", ++numPushTemp, val);
                temp.push(val);
            }

            //rotate matrix
            for (int j = 0; j < matrix[i].length; j++) {

                int val = temp.pop();
                System.out.printf("writing to m[%d,%d] val=%d%n", i, j, val);
                matrix[i][j] = val;
            }
        }
    }

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

    public static void main(String[] args) {
        A o = new A();
        int[][] matrix = {
                {3, 9, 8, 2 },
                {5, 5, 5, 1 },
                {4, 7, 6, 4 },
                {4, 1, 8, 2 }
        };
        o.dump(matrix);
        System.out.println("\n");
        o.go(matrix);
        o.dump(matrix);
    }
}