# 54. Spiral Matrix

## 15 Jan 54. Spiral Matrix

Given an `m x n` `matrix`, return all elements of the `matrix` in spiral order.

Example 1:

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

Example 2:

```Input: matrix = [[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]
```

Constraints:

• `m == matrix.length`
• `n == matrix[i].length`
• `1 <= m, n <= 10`
• `-100 <= matrix[i][j] <= 100`

python代码如下，核心是每次遇到新的边界时，顺时针修改移动方向，并且将老边界内移。

class Solution(object):
def spiralOrder(self, matrix):
“””
:type matrix: List[List[int]]
:rtype: List[int]
“””
if not matrix or not matrix[0]: return []
M, N = len(matrix), len(matrix[0])
left, right, up, down = 0, N – 1, 0, M – 1
res = []
x, y = 0, 0
dirs = [(0, 1), (1, 0), (0, -1), (-1, 0)]
cur_d = 0
while len(res) != M * N:
res.append(matrix[x][y])
if cur_d == 0 and y == right:
cur_d += 1
up += 1
elif cur_d == 1 and x == down:
cur_d += 1
right -= 1
elif cur_d == 2 and y == left:
cur_d += 1
down -= 1
elif cur_d == 3 and x == up:
cur_d += 1
left += 1
cur_d %= 4
x += dirs[cur_d][0]
y += dirs[cur_d][1]
return res
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class Solution(object):
def spiralOrder(self, matrix):
“””
:type matrix: List[List[int]]
:rtype: List[int]
“””
if not matrix or not matrix[0]: return []
m, n = len(matrix), len(matrix[0])
visited = [[0] * n for _ in range(m)]
res = []
self.row, self.col = 0, 0
def spiral():
move = False
while self.col < n and not visited[self.row][self.col]:
res.append(matrix[self.row][self.col])
visited[self.row][self.col] = 1
self.col += 1
move = True
self.col -= 1
self.row += 1
while self.row < m and not visited[self.row][self.col]:
res.append(matrix[self.row][self.col])
visited[self.row][self.col] = 1
self.row += 1
move = True
self.row -= 1
self.col -= 1
while self.col >= 0 and not visited[self.row][self.col]:
res.append(matrix[self.row][self.col])
visited[self.row][self.col] = 1
self.col -= 1
move = True
self.col += 1
self.row -= 1
while self.row >= 0 and not visited[self.row][self.col]:
res.append(matrix[self.row][self.col])
visited[self.row][self.col] = 1
self.row -= 1
move = True
self.row += 1
self.col += 1
if move:
spiral()
spiral()
return res

class Solution:
def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
if not matrix or not matrix[0]:
return []
m = len(matrix)
n = len(matrix[0])
count = m * n
left = 0
right = n-1
up = 0
down = m – 1
results = []
x = 0
y = 0
cur_d = 0
dirs = [(0,1), (1, 0), (0, -1), (-1, 0)]
while len(results) < count:
results.append(matrix[x][y])
if cur_d == 0 and y == right:
cur_d += 1
up += 1
elif cur_d == 1 and x == down:
cur_d += 1
right -= 1
elif cur_d == 2 and y == left:
cur_d += 1
down -= 1
elif cur_d == 3 and x == up:
cur_d += 1
left += 1

cur_d = cur_d % 4
x += dirs[cur_d][0]
y += dirs[cur_d][1]
return results