Max Rectangle
利用largest rectangle in histogram的方法，这题比较简单。
https://leetcode.com/discuss/97731/solution-largest-rectangle-histogram-solved-stack-simulation
class Solution:
# @param {character[][]} matrix
# @return {integer}
def maximalRectangle(self, matrix):
ret = 0
if not matrix: return 0
count = [0]* len(matrix[0]) + [-1]
for row in matrix:
for i in range(len(row)):
count[i] += 1
if row[i] == '0': count[i] = 0
st = [(-1,-1)]
for index, c in enumerate(count):
while st[-1][1] > c:
ii, cc = st.pop()
ret = max(ret, cc * (index - st[-1][0] - 1))
st.append((index, c))
return ret