LeetCode 835: Image Overlap Solution

Master LeetCode problem 835 (Image Overlap), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

835. Image Overlap

Medium

Array Matrix

Problem Explanation

Explanation:

To solve this problem, we can iterate over all possible translations of one image over the other and count the number of overlapping 1s. We can achieve this by trying all possible translations (left, right, up, down) and counting the overlapping 1s. The maximum count of overlapping 1s will give us the largest possible overlap.

Here is the step-by-step approach:

Iterate through all possible translations of img1 over img2.
For each translation, count the number of overlapping 1s by comparing the corresponding positions in both images.
Keep track of the maximum count of overlapping 1s.
Return the maximum count as the largest possible overlap.

Time Complexity: O(n^4) where n is the size of the input matrix Space Complexity: O(1)

Solution Code

class Solution {
    public int largestOverlap(int[][] img1, int[][] img2) {
        int n = img1.length;
        int maxOverlaps = 0;
        
        for (int rowOffset = -n + 1; rowOffset < n; rowOffset++) {
            for (int colOffset = -n + 1; colOffset < n; colOffset++) {
                int overlaps = 0;
                
                for (int i = 0; i < n; i++) {
                    for (int j = 0; j < n; j++) {
                        if ((i + rowOffset >= 0 && i + rowOffset < n) && (j + colOffset >= 0 && j + colOffset < n)) {
                            overlaps += img1[i][j] & img2[i + rowOffset][j + colOffset];
                        }
                    }
                }
                
                maxOverlaps = Math.max(maxOverlaps, overlaps);
            }
        }
        
        return maxOverlaps;
    }
}

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