面试题20：顺时针打印矩阵

链接：https://www.nowcoder.com/questionTerminal/9b4c81a02cd34f76be2659fa0d54342a
来源：牛客网

/**

 * @description 顺时针打印矩阵

 * @author GongchuangSu

 * @since 2016.09.03

 * @explain 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.

 */

import java.util.*;

 

public class Solution{

    ArrayList<Integer> list =new ArrayList<>();

     

    publicArrayList<Integer> printMatrix(int[][] matrix) {

        introws = matrix.length;

        intcolumns = matrix[0].length;

        intstart = 0;

        while(rows > start*2&& columns > start*2){

            printMatrixInCircle(matrix, rows, columns, start);

            start++;

        }

        returnlist;

    }

     

    /**

     * 功能：打印一圈

     */

    publicvoid printMatrixInCircle(int[][] matrix, introws, int columns, int start){

        // 从左到右打印一行

        for(inti = start; i < columns - start; i++)

            list.add(matrix[start][i]);

        // 从上到下打印一列

        for(intj = start + 1; j < rows - start; j++)

            list.add(matrix[j][columns - start -1]);

        // 从右到左打印一行

        for(intm = columns - start - 2; m >= start && rows - start -1 > start; m--)

            list.add(matrix[rows - start -1][m]);

        // 从下到上打印一列

        for(intn = rows - start - 2; n >= start +1 && columns - start -1 > start; n--)

            list.add(matrix[n][start]);

    }

}