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。

    示例 1：
    输入：matrix = [[1,2,3],[4,5,6],[7,8,9]] 输出：[1,2,3,6,9,8,7,4,5]
    示例 2：
    输入：matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]] 输出：[1,2,3,4,8,12,11,10,9,5,6,7]

    模拟注意边界问题，自己写的代码不够优雅

    1. class Solution {
    2.     public int[] spiralOrder(int[][] matrix) {
    3.         if(matrix.length == 0) return new int[0];
    4.         int l = 0, r = matrix[0].length - 1, t = 0, b = matrix.length - 1, x = 0;
    5.         int[] res = new int[(r + 1) * (b + 1)];
    6.         while(true) {
    7.             for(int i = l; i <= r; i++) res[x++] = matrix[t][i]; // left to right.
    8.             if(++t > b) break;
    9.             for(int i = t; i <= b; i++) res[x++] = matrix[i][r]; // top to bottom.
    10.             if(l > --r) break;
    11.             for(int i = r; i >= l; i--) res[x++] = matrix[b][i]; // right to left.
    12.             if(t > --b) break;
    13.             for(int i = b; i >= t; i--) res[x++] = matrix[i][l]; // bottom to top.
    14.             if(++l > r) break;
    15.         }
    16.         return res;
    17.     }
    18. }
    21. //自己写的
    22. class Solution {
    23.     public int[] spiralOrder(int[][] matrix) {
    24.         int m = matrix.length;
    25.         if(m == 0){
    26.             return new int[0];
    27.         }
    28.         int n = matrix[0].length;
    29.         int offset = 0;
    30.         int row = 0, col = 0;
    31.         int count = 0;
    32.         int [] res = new int[m * n];
    33.         while(true){
    34.             for(; col < n - offset; col++){
    35.                 res[count++] = matrix[row][col];
    36.             }
    37.             col--;
    38.             row++;
    39.             if(count == m*n)
    40.                 break;
    41.             for(; row < m - offset; row++){
    42.                   res[count++] = matrix[row][col];
    43.             }
    44.             row--;
    45.             col--;
    46.             if(count == m*n)
    47.                 break;
    48.             for(; col >= offset; col--){
    49.                   res[count++] = matrix[row][col];
    50.             }
    51.             col++;
    52.             row--;
    53.             if(count == m*n)
    54.                 break;
    55.             for(; row > offset; row--){
    56.                   res[count++] = matrix[row][col];
    57.             }
    58.             row++;
    59.             col++;
    60.             if(count == m*n)
    61.                 break;
    62.             offset++;
    63.         }
    65.         return res;
    66.     }
    67. }