题目链接：883. 三维形体投影面积
数学题，分别计算三个视图的面积，然后求和即可。
from typing import List
class Solution:
def projectionArea(self, grid: List[List[int]]) -> int:
m = len(grid)
if m == 0:
return 0
n = len(grid[0])
if n == 0:
return 0
xOy = sum(sum(1 if i > 0 else 0 for i in row) for row in grid)
xOz = sum(max(row) for row in grid)
yOz = sum(max(row) for row in zip(*grid))
return xOy + xOz + yOz