892. Surface Area of 3D Shapes

最新推荐文章于 2025-01-22 16:42:20 发布

SnailRunFast

最新推荐文章于 2025-01-22 16:42:20 发布

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本文介绍了一种算法，用于计算由1*1*1立方体堆叠在N*N网格上的三维形状的总表面面积。通过分析每个立方体对总面积的贡献，包括顶面、底面及侧面，实现了对不同形状的精确面积计算。

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892. Surface Area of 3D Shapes

Easy

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

Example 3:

Input: [[1,0],[0,2]]
Output: 16

Example 4:

Input: [[1,1,1],[1,0,1],[1,1,1]]
Output: 32

Example 5:

Input: [[2,2,2],[2,1,2],[2,2,2]]
Output: 46

Note:

1 <= N <= 50
0 <= grid[i][j] <= 50

class Solution {
    public int surfaceArea(int[][] grid) {
        int area = 0;
        int rows = grid.length;
        int columns = grid[0].length;
        
        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[i].length; j++) {
                if (grid[i][j] > 0) {
                    area += 2; // up, down
                    
                    if (0 == j) {
                        area += grid[i][j];
                    } else {
                        area += Math.max(0, grid[i][j] - grid[i][j - 1]);
                    }
                    
                    if (j + 1 == columns) {
                        area += grid[i][j];
                    } else {
                        area += Math.max(0, grid[i][j] - grid[i][j + 1]);
                    }
                    
                    if (0 == i) {
                        area += grid[i][j];
                    } else {
                        area += Math.max(0, grid[i][j] - grid[i - 1][j]);
                    }
                    
                    if (i + 1 == rows) {
                        area += grid[i][j];
                    } else {
                        area += Math.max(0, grid[i][j] - grid[i + 1][j]);
                    }
                }
            }
        }
        
        return area;
    }
}