Maximum Matrix Sum — LeetCode 1975 Python Solution

The problem

You are given an n x n integer matrix. You can do the following operation any number of times: Choose any two adjacent elements of matrix and multiply each of them by -1.

Example

Input

matrix = [[1,-1],[-1,1]]

Output

4

Explanation

We can follow the following steps to reach sum equals 4:

Python solution

class Solution:
    def maxMatrixSum(self, matrix: List[List[int]]) -> int:
        mi = inf
        s = cnt = 0
        for row in matrix:
            for x in row:
                cnt += x < 0
                y = abs(x)
                mi = min(mi, y)
                s += y
        return s if cnt % 2 == 0 else s - mi * 2

Complexity

Pattern: Matrix and Grid

Treat a 2-D grid as a graph whose neighbours are the four adjacent cells. LeetCode 1975. Maximum Matrix Sum is filed here because LeetCode tags it Matrix, which is the vocabulary this hub collects.

The matrix and grid guide has the Python template for the pattern and the 216 LeetCode problems that use it.

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