class Solution(object):
def spiral(self, matrix):
"""
input: int[][] matrix
return: Integer[]
"""
if (len(matrix)==0):
return []
# write your solution here
nrow = len(matrix)
ncol = len(matrix[0])
res = []
# every round handle an outer loop
upper = 0
lower = nrow-1
left = 0
right = ncol-1 # inclusive
while(True):
# 1. print the upper boundary
for c in range(left,right+1):
res.append(matrix[upper][c])
upper += 1
if (upper > lower):
break
# 2. print the right boundary
for r in range(upper, lower+1):
res.append(matrix[r][right])
right -= 1
if (right < left):
break
# 3. print the lower boundary
for c in range(right, left-1, -1):
res.append(matrix[lower][c])
lower -= 1
if (upper > lower):
break
# 4. print the left boundary
for r in range(lower, upper-1, -1):
res.append(matrix[r][left])
left += 1
if (right < left):
break
return res
Note the empty case here.
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