P127、面试题20：顺时针打印矩阵

题目：输入一个矩阵，按照从外向里以顺时针的顺序依次打印出每一个数字。例如：如果输入如下矩阵：
1  2  3  4 
5  6  7  8
9  10  11  12
13  14  15  16
则依次打印出数字1、2、3、4、8、12、16、15、14、13、9、5、6、7、11、10。

测试用例：

数组有多行多列，数组只有一行，数组中只有一列，数组中只有一行一列

 

代码实现：

package com.yyq;

/**
 * Created by Administrator on 2015/9/16.
 */
public class PrintMatrix {
    public static void printMatrixClockwisely(int[][] numbers, int columns, int rows){
        if (numbers == null  || columns < 0 || rows < 0){
            return;
        }
        int start = 0;
        while(columns > start * 2 && rows > start * 2){
            printMatrixInCircle(numbers,columns,rows,start);
            start ++;
        }
    }
    public static void printMatrixInCircle(int[][] numbers, int columns, int rows, int start){
        int endX = columns - 1 - start;
        int endY = rows - 1 - start;
        //从左到右打印一行
        for (int i = start; i <= endX; i++){
            int number = numbers[start][i];
            printNumber(number);
        }
        //从上到下打印一列
        if (start < endY){
            for (int i = start+1; i <= endY; i++){
                int number = numbers[i][endX];
                printNumber(number);
            }
        }
        //从右到左打印一行
        if (start < endX && start < endY){
            for (int i = endX - 1; i >= start; i--){
                int number = numbers[endY][i];
                printNumber(number);
            }
        }
        if (start < endX && start < endY - 1){
            for (int i = endY - 1; i >= start+1; i--){
                int number = numbers[i][start];
                printNumber(number);
            }
        }
    }
    public static void printNumber(int number){
        System.out.print(number+"\t");
    }

    // ====================测试代码====================
    public static void Test(String testName, int columns, int rows)
    {
        System.out.println(testName+" Begin: " + columns + " columns, " + rows + " rows.");
        if(columns < 1 || rows < 1)
            return;

        int[][] numbers = new int[rows][columns];
        for(int i = 0; i < rows; ++i)
        {
            for(int j = 0; j < columns; ++j)
            {
                numbers[i][j] = i * columns + j + 1;
            }
        }
        printMatrixClockwisely(numbers, columns, rows);
        System.out.println("");
    }

    public static void main(String[] args){
    /*
    1
    */
        Test("test1",1, 1);

    /*
    1    2
    3    4
    */
        Test("test2",2, 2);

    /*
    1    2    3    4
    5    6    7    8
    9    10   11   12
    13   14   15   16
    */
        Test("test3",4, 4);

    /*
    1    2    3    4    5
    6    7    8    9    10
    11   12   13   14   15
    16   17   18   19   20
    21   22   23   24   25
    */
        Test("test4",5, 5);

    /*
    1
    2
    3
    4
    5
    */
        Test("test5",1, 5);

    /*
    1    2
    3    4
    5    6
    7    8
    9    10
    */
        Test("test6",2, 5);

    /*
    1    2    3
    4    5    6
    7    8    9
    10   11   12
    13   14   15
    */
        Test("test7",3, 5);

    /*
    1    2    3    4
    5    6    7    8
    9    10   11   12
    13   14   15   16
    17   18   19   20
    */
        Test("test8",4, 5);

    /*
    1    2    3    4    5
    */
        Test("test9",5, 1);

    /*
    1    2    3    4    5
    6    7    8    9    10
    */
        Test("test10",5, 2);

    /*
    1    2    3    4    5
    6    7    8    9    10
    11   12   13   14    15
    */
        Test("test11",5, 3);

    /*
    1    2    3    4    5
    6    7    8    9    10
    11   12   13   14   15
    16   17   18   19   20
    */
        Test("test12",5, 4);

        Test("test13",0,0);
    }
}

 

输出结果：

test1 Begin: 1 columns, 1 rows.

1

test2 Begin: 2 columns, 2 rows.

1 2 4 3

test3 Begin: 4 columns, 4 rows.

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

test4 Begin: 5 columns, 5 rows.

1 2 3 4 5 10 15 20 25 24 23 22 21 16 11 6 7 8 9 14 19 18 17 12 13

test5 Begin: 1 columns, 5 rows.

1 2 3 4 5

test6 Begin: 2 columns, 5 rows.

1 2 4 6 8 10 9 7 5 3

test7 Begin: 3 columns, 5 rows.

1 2 3 6 9 12 15 14 13 10 7 4 5 8 11

test8 Begin: 4 columns, 5 rows.

1 2 3 4 8 12 16 20 19 18 17 13 9 5 6 7 11 15 14 10

test9 Begin: 5 columns, 1 rows.

1 2 3 4 5

test10 Begin: 5 columns, 2 rows.

1 2 3 4 5 10 9 8 7 6

test11 Begin: 5 columns, 3 rows.

1 2 3 4 5 10 15 14 13 12 11 6 7 8 9

test12 Begin: 5 columns, 4 rows.

1 2 3 4 5 10 15 20 19 18 17 16 11 6 7 8 9 14 13 12

test13 Begin: 0 columns, 0 rows.