Question

我做了一个小程序，用一些递归来计算矩阵的行列式。我尝试了5x5矩阵并出现了堆栈溢出错误。我知道递归可能太深了，但我对如何补救它感到迷茫。任何解决方案？

这是我的代码：

/**
 * @requires matrix is at least 2x2 and has all real entries
 * @param matrix[][] a matrix
 * @param row is the row to be omitted
 * @param col is the column to be omitted
 * @requires @code col and @code row are 
 * @returns the @code matrix without column
 */
private static int[][] subMatrix(int[][] matrix, int row, int col){
    int[][] newMatrix = new int[matrix.length][matrix[0].length];
    int newRow = 0;
    for ( int i = 0; i < matrix.length; i++){
        int newCol = 0;
        if ( i != row ){
            for( int j = 0; j < matrix[i].length; j++){
                if ( j != 0){
                    newMatrix[i][j] = matrix[newRow][newCol];
                    newCol++;
                }
            }
            newRow++;
        }

    }
    return newMatrix;
}
/**
 * @requires matrix is at least 2x2 and has all real entries
 * @param matrix[][] a matrix
 * @returns the determinant of @code matrix
 */
private static int det(int[][] matrix){
    int det = 0;
    int rows = matrix.length;
    int cols = matrix[0].length;

    //handling base case
    if(rows == 2 & cols == 2){
        det = matrix[0][0]*matrix[1][1] - matrix[0][1]*matrix[1][0];
    } else {
        //expanding a row
        if(rows > cols)
        {
            for(int i = 0; i < rows; i++){
                det += matrix[0][i]*det(subMatrix(matrix, i, 0));
            }
        }
        //expanding a column
        else {
            for(int i = 0; i < rows; i++){
                det += matrix[i][0]*det(subMatrix(matrix, 0, i));
            }
        }
    }
    return det;
}
/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    System.out.print("Enter the number of rows: ");
    int rows = in.nextInt();
    System.out.print("Enter the number of columns: ");
    int cols = in.nextInt();

    //reading in matrix
    int[][] matrix = new int[rows][cols];
    for(int i = 0; i < rows; i++){
        System.out.print("Enter the entries of row " + i + ": ");
        for (int j = 0; j < cols; j++){
            matrix[i][j] = in.nextInt();
        }
    }
    System.out.println("The determinant of the matrix is: " + det(matrix));
}

Answer 1

这会导致问题（下一行是相关的）：

int[][] newMatrix = new int[matrix.length][matrix[0].length];

您实际上创建了与原始大小完全相同的子矩阵，然后应用递归。

我假设您要创建完全排除row和col的子矩阵，因此每个维度的尺寸小一个，并将内容移到左侧和顶部指定row和col。

我的程序给了我一个StackOverflowError

1 个答案: