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class Solution {
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 public:
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  int surfaceArea(vector<vector<int>> &grid) {
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    int area = 0;
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    for (int i = 0; i < grid.size(); i++) {
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      for (int j = 0; j < grid[0].size(); j++) {
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        // adding 4 sides
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        area += grid[i][j] * 4;
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        // adding two because of there will only one top and one bottom if cube
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        // is placed upon each other
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        if (grid[i][j] != 0) area += 2;
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        // subtracting adjacent side area if any
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        if (i - 1 >= 0) area -= min(grid[i - 1][j], grid[i][j]);
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        if (i + 1 < grid.size()) area -= min(grid[i + 1][j], grid[i][j]);
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        if (j - 1 >= 0) area -= min(grid[i][j - 1], grid[i][j]);
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        if (j + 1 < grid.size()) area -= min(grid[i][j + 1], grid[i][j]);
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      }
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    }
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    return area;
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  }
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};