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