## Description

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]


## Solutions

### 1. Coding Skill

会改变原始的 matrix：

from typing import List
# @lc code=start
# Time: O(mn)
# Space: O(n)
class Solution:
def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
res = []
while matrix:
res += matrix.pop(0)  # left to right
if matrix and matrix[0]:  # top to down
for row in matrix:
res.append(row.pop())
if matrix:  # right to left
res += matrix.pop()[::-1]
if matrix and matrix[0]:  # bottom to up
for row in matrix[::-1]:
res.append(row.pop(0))
return res
# 22/22 cases passed (28 ms)
# Your runtime beats 61 % of python3 submissions
# Your memory usage beats 100 % of python3 submissions (12.8 MB)


### 2. Coding Skill

class Solution:
def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
res = []
if not matrix or not matrix[0]:
return res
top, bottom, left, right = 0, len(matrix) - 1, 0, len(matrix[0]) - 1

while True:
for i in range(left, right + 1):
res.append(matrix[top][i])
top += 1
if left > right or top > bottom:
break
for i in range(top, bottom + 1):
res.append(matrix[i][right])
right -= 1
if left > right or top > bottom:
break
for i in range(right, left - 1, -1):
res.append(matrix[bottom][i])
bottom -= 1
if left > right or top > bottom:
break
for i in range(bottom, top - 1, -1):
res.append(matrix[i][left])
left += 1
if left > right or top > bottom:
break
return res
# 22/22 cases passed (28 ms)
# Your runtime beats 61 % of python3 submissions
# Your memory usage beats 100 % of python3 submissions (12.8 MB)