# Leetcode 883. Projection Area of 3D Shapes

**Explanation**
---------------

front-back projection area on xz = `sum(max value for every col)`
right-left projection area on yz = `sum(max value for every row)`
top-down projection area on xy = `sum(1 for every v > 0)`

**Diagram**
-----------

I drawn this diagram to help understand.
**Complexity**
--------------

Time `O(N^2)` for one pass.
Space `O(1)` extra space.

class Solution:
    def projectionArea(self, grid: List[List[int]]) -> int:
        rows = len(grid)
        cols = len(grid[0])
        output = 0
        for row in range(rows):
            xz = 0
            yz = 0
            for col in range(cols):
                if grid[row][col] > 0:
                    output += 1
                xz = max(xz,grid[row][col])
                yz = max(yz,grid[col][row])
            output += xz
            output += yz

        return output