怎么形成以下数组并打印出来

/** * “蛇形矩阵” 计算及打印 * @author SageZk * @version 1.0 */public class Sp {    public static void main(String[] args) {        //方阵计算        final int LEN = 69;  //元素个数        final int SIDE = (int) Math.ceil(Math.sqrt(LEN));        final int[][] M = new int[SIDE][SIDE];        for (int i = 1, r = 0, c = 0, flag = 'c'; i <= LEN;) {            M[r][c] = i++;            if (r == 0) {                if (c % 2 == 0) ++c;                else ++r;                continue;            }            if (c == 0) {                if (r % 2 == 1) ++r;                else ++c;                continue;            }            switch (flag) {            case 'c':                if (c % 2 == 0) {                    --r;                } else {                    if (M[r][c - 1] != 0) {                        ++r;                    } else {                        --c;                        flag = 'r';                    }                }                break;            case 'r':                if (r % 2 == 1) {                    --c;                } else {                    if (M[r - 1][c] != 0) {                        ++c;                    } else {                        --r;                        flag = 'c';                    }                }                break;            }        }        //打印输出        final int PWIDTH = Integer.toString(LEN, 10).length();        final String FORMAT = "%0$" + PWIDTH + "d ";        final String FSPACE = "%0$" + PWIDTH + "s ";        for (int r = 0; r < M.length; ++r) {            for (int c = 0; c < M[r].length; ++c) {                if (M[r][c] == 0) {                    System.out.printf(FSPACE, "");                } else {                    System.out.printf(FORMAT, M[r][c]);                }            }            System.out.println();        }    }}