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.1test2 Begin: 2 columns, 2 rows.1 2 4 3test3 Begin: 4 columns, 4 rows.1 2 3 4 8 12 16 15 14 13 9 5 6 7 11 10test4 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 13test5 Begin: 1 columns, 5 rows.1 2 3 4 5test6 Begin: 2 columns, 5 rows.1 2 4 6 8 10 9 7 5 3test7 Begin: 3 columns, 5 rows.1 2 3 6 9 12 15 14 13 10 7 4 5 8 11test8 Begin: 4 columns, 5 rows.1 2 3 4 8 12 16 20 19 18 17 13 9 5 6 7 11 15 14 10test9 Begin: 5 columns, 1 rows.1 2 3 4 5test10 Begin: 5 columns, 2 rows.1 2 3 4 5 10 9 8 7 6test11 Begin: 5 columns, 3 rows.1 2 3 4 5 10 15 14 13 12 11 6 7 8 9test12 Begin: 5 columns, 4 rows.1 2 3 4 5 10 15 20 19 18 17 16 11 6 7 8 9 14 13 12test13 Begin: 0 columns, 0 rows.