leetcode 892. 三维形体的表面积
思路:bfs
只要某个点上有立方体,那么最下面和最上面一定能共享2.至于侧面能否有共享,只需要看周围的4个方向的高度即可。
class Solution {
public:
int surfaceArea(vector<vector<int>>& grid) {
int dr[]{0, 1, 0, -1};
int dc[]{1, 0, -1, 0};
int N = grid.size();
int ans = 0;
for (int r = 0; r < N; ++r)
for (int c = 0; c < N; ++c)
if (grid[r][c] > 0) {
ans += 2;
for (int k = 0; k < 4; ++k) {
int nr = r + dr[k];
int nc = c + dc[k];
int nv = 0;
if (0 <= nr && nr < N && 0 <= nc && nc < N)
nv = grid[nr][nc];
ans += max(grid[r][c] - nv, 0);
}
}
return ans;
}
};
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