2373 Largest Local Values in a Matrix

Fairly easy to overthink this problem. I mean no issues if you want to further analyze it and but it’s an easy.

Think of the problem as in that you need to iterate 9 total values for every value in the result matrix maxLocal.

Code:

Python

class Solution:
    def largestLocal(self, grid: List[List[int]]) -> List[List[int]]:
        n = len(grid)
        maxLocal = [[-1 for _ in range(n-2)] for _ in range(n-2)]
 
        for i in range(n-2):
            for j in range(n-2):
                for x in range(i, i+3):
                    for y in range(j, j+3):
                        maxLocal[i][j] = max(maxLocal[i][j], grid[x][y])
 
 
        return maxLocal

Big O Analysis

• Runtime The runtime complexity here is $O(N^2)$ , there’s a constant factor of 9 with each iteration, but we don’t usually count the constants.
• Memory The memory usage is O(N-2) where N = rows * cols for the original input matrix.

— A

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