Approach #1: Iterate Through Grid
Intuition and Algorithm
For each cell in the grid, look at the immediate neighbors  up to 9 of them, including the original cell.
Then, we will add the sum of the neighbors into ans[r][c]
while recording count
, the number of such neighbors. The final answer is the sum divided by the count.
Complexity Analysis

Time Complexity: , where is the number of pixels in our image. We iterate over every pixel.

Space Complexity: , the size of our answer.
Analysis written by: @awice.