题目要求
On a N * N grid, we place some 1 * 1 * 1 cubes that are axis-aligned with the x, y, and z axes.
Each value v = grid[i][j] represents a tower of v cubes placed on top of grid cell (i, j).
Now we view the projection of these cubes onto the xy, yz, and zx planes.
A projection is like a shadow, that maps our 3 dimensional figure to a 2 dimensional plane.
Here, we are viewing the "shadow" when looking at the cubes from the top, the front, and the side.
Return the total area of all three projections.
题目分析及思路
题目给出了一个方阵，方阵里面的数值是柱子的高度，求三视图所有的阴影部分的面积。俯视图投影就是不为0的柱子的个数，主视图、侧视图是当前视图柱子的最高值求和。
python代码
class Solution:
def projectionArea(self, grid):
"""
:type grid: List[List[int]]
:rtype: int
"""
top, front, side = 0, 0, 0
l = len(grid)
for i in range(l):
x, y = 0, 0
for j in range(l):
if grid[i][j] != 0:
top += 1
x = max(x, grid[i][j])
y = max(y, grid[j][i])
front += x
side += y
return top + front + side