描述
On a N * N grid, we place some 1 * 1 * 1 cubes.
Each value v = grid[i][j] represents a tower of v cubes placed on top of grid cell (i, j).
Return the total surface area of the resulting shapes.
Example 1:
Input: [[2]]
Output: 10
Example 2:
Input: [[1,2],[3,4]]
Output: 34
Note:
1 <= N <= 50
0 <= grid[i][j] <= 50
解析
根据题意，这道题和之前的 883. Projection Area of 3D Shapes 这道题有点类似，但是思路不一样，这道题要先计算总的表面积，再减去 2 倍的重复部分的表面积即可，时间复杂度为 O(N^2)，空间复杂度为 O(1)。
解答
class Solution(object):
def surfaceArea(self, grid):
"""
:type grid: List[List[int]]
:rtype: int
"""
result = 0
for i in range(len(grid)):
for j in range(len(grid[0])):
if grid[i][j]: result += 4*grid[i][j]+2
if i: result -= min(grid[i][j],grid[i-1][j])*2
if j: result -= min(grid[i][j],grid[i][j-1])*2
return result
运行结果
Runtime: 68 ms, faster than 86.11% of Python online submissions for Surface Area of 3D Shapes.
Memory Usage: 11.8 MB, less than 56.25% of Python online submissions for Surface Area of 3D Shapes.
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