題目：給定一個數組，將該陣列從第一個元素開始順時針打印出來。

分析：先考慮列印周圍一圈的問題，然後可以使用遞迴求解，直到最後全都列印完為止。也就是先列印最外圍的數，然後對於元二維陣列中間的陣列作為一個新的陣列，重新列印該新陣列的外圍的數，直到最後全部列印完為止。
程式碼如下：

package problem2;

/**
 * @author Hutongling
 */
public class 順時針列印二維陣列 {
    static void print2DArray(int data[][]) {
        if (data[0].length == 1) {
            for
 
 (int i = 0; i < data.length; i++)
                System.out.print(data[i][0] + " ");
            return;
        } else if (data.length == 1 && data[0].length != 1) {
            for (int i = 0; i < data[0].length; i++) 
                System.out.print(data[0][i] + " ");
            return
 
;
        } else if (data.length > 1) {
            int row = data.length;
            int column = data[0].length;
            int i = 0;
            for (i = 0; i < column; i++)
                System.out.print(data[0][i] + " ");
            for (i = 1; i < row; i++)
                System.out
 
.print(data[i][column - 1] + " ");
            for (i = column - 2; i >= 0; i--)
                System.out.print(data[row - 1][i] + " ");
            for (i = row - 2; i >= 1; i--)
                System.out.print(data[i][0] + " ");
            if (row - 2 > 0 && column - 2 > 0) {
                int subData[][] = new int[row - 2][column - 2];
                for (i = 1; i < row - 1; i++)
                    for (int j = 1; j < column - 1; j++)
                        subData[i - 1][j - 1] = data[i][j];
                data = null;
                print2DArray(subData);
            }
        }

    }

    public static void main(String[] args) {
        int data0[][] = {{1, 2, 3, 4, 5, 6 }};
        int data[][] = { { 1, 2, 3, 4, 5, 6 }, { 2, 3, 4, 5, 6, 7 }, { 3, 4, 5, 6, 7, 8 }, { 4, 5, 6, 7, 8, 9 } };
        int data1[][] = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 }, { 13, 14, 15, 16 } };
        int data2[][] = { { 1, 2, 3, 4, 5 }, { 2, 3, 4, 5, 6 }, { 3, 4, 5, 6, 7 }, { 4, 5, 6, 7, 8 }, { 5, 6, 7, 8, 9 } };
        int data3[][]={{1},{2},{3},{4}};
        print2DArray(data0);
        System.out.println();
        print2DArray(data);
        System.out.println();
        print2DArray(data1);
        System.out.println();
        print2DArray(data2);
        System.out.println();
        print2DArray(data3);
    }

}

結果如下：
1 2 3 4 5 6
1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 3 4 5 6 7 6 5 4
1 2 3 4 8 12 16 15 14 13 9 5 6 7 11 10
1 2 3 4 5 6 7 8 9 8 7 6 5 4 3 2 3 4 5 6 7 6 5 4 5
1 2 3 4