Largest Rectangle in Histogram

1def largestRectangleArea(heights):
2  stack = []
3  max_area = 0
4
5  for i in range(len(heights)):
6    while stack and heights[i] < heights[stack[-1]]:
7      height = heights[stack.pop()]
8      width = i if not stack else i - stack[-1] - 1
9      current_area = height * width
10      max_area = max(max_area, current_area)
11
12    stack.append(i)
13
14  while stack:
15    height = heights[stack.pop()]
16    width = len(heights) if not stack else len(heights) - stack[-1] - 1
17    current_area = height * width
18    max_area = max(max_area, current_area)
19
20  return max_area