【剑指OFFER】顺时针打印矩阵

【问题描述】

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4 X 4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.

 

【AC代码】

import java.util.ArrayList;
public class Solution {
    public ArrayList<Integer> printMatrix(int [][] matrix) {
       ArrayList<Integer> list = new ArrayList<>();
       int row = matrix.length, column = matrix[0].length;
       if (row == 0 || column == 0) return null;
       int up = 0, down = row-1, left = 0, right = column-1;
       while (true) {
           for (int c = left; c <= right; c++) {
               list.add(matrix[up][c]);
           }
           
           up++;
           if (up > down) break;
           for (int r = up; r <= down; r++) {
               list.add(matrix[r][right]);
           }
           
           right--;
           if (right < left) break;
           for (int c = right; c >= left; c--) {
               list.add(matrix[down][c]);
           }
           
           down--;
           if (down < up) break;
           for (int r = down; r >= up; r--) {
               list.add(matrix[r][left]);
           }
           
           left++;
           if (left > right) break;
       }
        return list;
    }
}