Image Overlap

Two images A and B are given, represented as binary, square matrices of the same size. (A binary matrix has only 0s and 1s as values.)

We translate one image however we choose (sliding it left, right, up, or down any number of units), and place it on top of the other image. After, the overlap

(Note also that a translation does not include any kind of rotation.)

What is the largest possible overlap?

Example 1:

Input: A = [[1,1,0],
            [0,1,0],
            [0,1,0]]
       B = [[0,0,0],
            [0,1,1],
            [0,0,1]]
Output: 3
Explanation: We slide A to right by 1 unit and down by 1 unit.
 

Notes:

1. 1 <= A.length = A[0].length = B.length = B[0].length <= 30
2. 0 <= A[i][j], B[i][j] <= 1

 1 class Solution {
 2 public:
 3     int largestOverlap(vector<vector<int>>& A, vector<vector<int>>& B) {
 4         int n = A.size();
 5         int res = 0;
 6         for
 
(int i = -n+1; i < n; i++){
 7             for(int j =-n+1; j < n; j++){
 8                 int count = 0;
 9                 for(int k = max(i,0); k < min(n+i,n); k++){
10                     for(int l = max(j,0); l < min(n+j,n);l++){
11                         if(A[k-i][l-j]==1&&B[k][l]==1){
12                             count++;
13                         }
14                     }
15                 }
16                 res = max(res,count);
17             }
18         }
19         return res;
20     }
21 };

暴力模擬，O(n⁴),模擬過程的邊界以及max的使用也沒有想象中的那麽容易。

835. Image Overlap —— weekly contest 84