LeetCode 883 三维形体投影面积[数学] HERODING的LeetCode之路

解题思路：
本次每日一题题目描述极其不清，其实就是对于n*n的物体，求其三个投影的面积和，也就是底面积（该位置是否有方块）+每行最高的和+每列最高的和，代码如下：

class Solution {
public:
    int projectionArea(vector>& grid) {
        int n = grid.size();
        int xyArea = 0, xzArea = 0, yzArea = 0;
        for(int i = 0; i < n; i ++) {
            int xzHigh = 0, yzHigh = 0;
            for(int j = 0; j < n; j ++) {
                xyArea += grid[i][j] == 0 ? 0 : 1;
                xzHigh = max(xzHigh, grid[i][j]);
                yzHigh = max(yzHigh, grid[j][i]);
            }
            xzArea += xzHigh;
            yzArea += yzHigh;
        }
        return xzArea + xyArea + yzArea;
    }
};