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Maximal_Rectangle.py
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Maximal_Rectangle.py
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Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area.
# Analysis: maintain a row length of Integer array H recorded its height of '1's,
# and scan and update row by row to find out the largest rectangle of each row.
class Solution:
# @param matrix, a list of lists of 1 length string
# @return an integer
def maximalRectangle(self, matrix):
if len(matrix) == 0 or len(matrix[0]) == 0:
return 0
row = len(matrix)
cal = len(matrix[0]) + 1
result = 0
height = [0 for _ in xrange(cal)]
for i in xrange(row):
stack = []
for j in xrange(cal):
if j < cal - 1:
if matrix[i][j] == "1": # Note: here we should determine whether matrix[i][j]=='1' or not
height[j] += 1
else:
height[j] = 0
while stack and height[stack[-1]] >= height[j]: # 注意这里要用while !!!否则只计算了一次的面积
h_index = stack.pop()
ht = height[h_index]
if stack:
width = j - stack[-1] - 1
else:
width = j
result = max(result, ht*width)
stack.append(j)
return result
'''
Note1 : need to use "while" not "if"
Input:
["01101","11010","01110","11110","11111","00000"]
Output:
5
Expected:
9
'''