54. Spiral Matrix
Array, Matrix, Simulation, AMateList ·Problem Statement
link: https://leetcode.com/problems/spiral-matrix/description/ https://leetcode.cn/problems/spiral-matrix/description/
Given an m x n matrix, return all elements of the matrix in spiral order.
Example:
Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [1,2,3,6,9,8,7,4,5]
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]
Solution Approach
Algorithm
Implement
class Solution:
def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
# do simulate
# l, r, t, b
# loop:
# l -> r end i <= r move t : if t > b break
# t -> b end j <= b move r : if r < l break
# r -> l end i >= l move b : if b > t break
# b -> t end j <= t move l : if l > r break
if not matrix:
return []
l, r, t, b, res = 0, len(matrix[0]) - 1, 0, len(matrix) - 1, []
while True:
for i in range(l, r + 1): res.append(matrix[t][i])
t += 1
if t > b:
break
for j in range(t, b + 1):
res.append(matrix[j][r])
r -= 1
if r < l:
break
for i in range(r, l - 1, -1):
res.append(matrix[b][i]) #细节方向不要错
b -= 1
if t > b:
break
for j in range(b, t - 1, -1):
res.append(matrix[j][l])
l += 1
if l > r:
break
return res