54. Spiral Matrix

{leetcode}/problems/spiral-matrix/[LeetCode - Spiral Matrix^]

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

Example 1:

Input:
[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]
Output: [1,2,3,6,9,8,7,4,5]

Example 2:

Input:
[
  [1, 2, 3, 4],
  [5, 6, 7, 8],
  [9,10,11,12]
]
Output: [1,2,3,4,8,12,11,10,9,5,6,7]

思路分析

从回溯思想得到启发，使用递归来逐层推进。每次方法调用只负责指定层的遍历，向里推进层次的工作，交给递归来完成。这样避免了复杂的判断。

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一刷

link:{sourcedir}/_0054_SpiralMatrix.java[role=include]

二刷

link:{sourcedir}/_0054_SpiralMatrix_2.java[role=include]