Maximum Rectangle

Problem Description
Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area.
Solutions
I. Solution by finding largest rectangle in histogram

class Solution:
    # @param matrix, a list of lists of 1 length string
    # @return an integer
    def maximalRectangle(self, matrix):
        if not matrix:
            return 0
        h, w = len(matrix), len(matrix[0])
        m = [[0]*w for _ in range(h)]
        for j in range(h):
            for i in range(w):
                if matrix[j][i] == '1':
                    m[j][i] = m[j-1][i] + 1
        return max(self.largestRectangleArea(row) for row in m)
    
    def largestRectangleArea(self, height):
        '''
        This uses the way we calculate maximum rectangle in histogram
        '''
        height.append(0)
        stack, area = [], 0
        for i in range(len(height)):
            while stack and height[stack[-1]] > height[i]:
                h = height[stack.pop()]
                w = i if not stack else i-stack[-1]-1
                area = max(area, h*w)
            stack.append(i)
        return area