835 - Image Overlap\.

Medium

You are given two images, img1 and img2, represented as binary, square matrices of size n x n. A binary matrix has only 0s and 1s as values.

We translate one image however we choose by sliding all the 1 bits left, right, up, and/or down any number of units. We then place it on top of the other image. We can then calculate the overlap by counting the number of positions that have a 1 in both images.

Note also that a translation does not include any kind of rotation. Any 1 bits that are translated outside of the matrix borders are erased.

Return the largest possible overlap.

Example 1:

Input: img1 = \[\[1,1,0],0,1,0,0,1,0], img2 = \[\[0,0,0],0,1,1,0,0,1]

Output: 3

Explanation: We translate img1 to right by 1 unit and down by 1 unit. The number of positions that have a 1 in both images is 3 (shown in red).

Example 2:

Input: img1 = \[\[1]], img2 = \[\[1]]

Output: 1

Example 3:

Input: img1 = \[\[0]], img2 = \[\[0]]

Output: 0

Constraints:

• n == img1.length == img1[i].length

• n == img2.length == img2[i].length

• 1 <= n <= 30

• img1[i][j] is either 0 or 1.

• img2[i][j] is either 0 or 1.