<p>An <strong>image smoother</strong> is a filter of the size <code>3 x 3</code> that can be applied to each cell of an image by rounding down the average of the cell and the eight surrounding cells (i.e., the average of the nine cells in the blue smoother). If one or more of the surrounding cells of a cell is not present, we do not consider it in the average (i.e., the average of the four cells in the red smoother).</p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/05/03/smoother-grid.jpg" style="width: 493px; height: 493px;" />
<p>Given an <code>m x n</code> integer matrix <code>img</code> representing the grayscale of an image, return <em>the image after applying the smoother on each cell of it</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/05/03/smooth-grid.jpg" style="width: 613px; height: 253px;" />
<pre>
<strong>Input:</strong> img = [[1,1,1],[1,0,1],[1,1,1]]
<strong>Output:</strong> [[0,0,0],[0,0,0],[0,0,0]]
<strong>Explanation:</strong>
For the points (0,0), (0,2), (2,0), (2,2): floor(3/4) = floor(0.75) = 0
For the points (0,1), (1,0), (1,2), (2,1): floor(5/6) = floor(0.83333333) = 0
For the point (1,1): floor(8/9) = floor(0.88888889) = 0
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/05/03/smooth2-grid.jpg" style="width: 613px; height: 253px;" />
<pre>
<strong>Input:</strong> img = [[100,200,100],[200,50,200],[100,200,100]]
<strong>Output:</strong> [[137,141,137],[141,138,141],[137,141,137]]
<strong>Explanation:</strong>
For the points (0,0), (0,2), (2,0), (2,2): floor((100+200+200+50)/4) = floor(137.5) = 137
For the points (0,1), (1,0), (1,2), (2,1): floor((200+200+50+200+100+100)/6) = floor(141.666667) = 141
For the point (1,1): floor((50+200+200+200+200+100+100+100+100)/9) = floor(138.888889) = 138
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == img.length</code></li>
	<li><code>n == img[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 200</code></li>
	<li><code>0 &lt;= img[i][j] &lt;= 255</code></li>
</ul>

class Solution {
public:
    /**
     * Calculates average of the cell and its surrounding neighbors. 
     * 
     * @param img The image grid to search.
     * @param row Current row of cell.
     * @param col Current column of cell.
     * @return The floored average of the cell and its surrounding neighbors.
     */
    int getAverageOfCellNeighbors(vector<vector<int>>& img, int row, int col) {
        int sum = 0, count = 0;

        for(int i = -1; i <= 1; i++) {
            for(int j = -1; j <= 1; j++) {
                if(row + i < 0 || row + i >= img.size()) continue;
                if(col + j < 0 || col + j >= img[0].size()) continue;
                sum += img[row + i][col + j];
                count++;
            }
        }
        
        return sum / count;
    }

    /**
     * Smooths image by rounding down the average of the cell and the eight surrounding cells. 
     * 
     * @param img The image grid to smooth.
     * @return A smoothed image.
     */
    vector<vector<int>> imageSmoother(vector<vector<int>>& img) {
        vector<vector<int>> resultImg;

        for(int i = 0; i < img.size(); i++) {
            resultImg.push_back(vector<int>());
            for(int j = 0; j < img[0].size(); j++) {
                resultImg[i].push_back(getAverageOfCellNeighbors(img, i, j));
            }
        }

        return resultImg;
    }
};
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