LeetCode Entry

1975. Maximum Matrix Sum

05.01.2026 medium 2026 kotlin rust

Max sum after multiply -1 adjacent cells

1975. Maximum Matrix Sum medium blog post substack youtube

Join me on Telegram

https://t.me/leetcode_daily_unstoppable/1226

Problem TLDR

Max sum after multiply -1 adjacent cells #medium #brainteaser

Intuition

Notice that we can move “-“ to any cell in the matrix. Count “-“, find sum and find minimum value to subtract.

    // we can propagate - to any cell
    // if even -- count then all positive
    // otherwise make it the smallest abs

Approach

• don’t forget to subtract 2*min

Complexity

• Time complexity: \(O(m)\)

• Space complexity: \(O(1)\)

Code

// 9ms
    fun maxMatrixSum(m: Array<IntArray>): Long {
        var cnt = 0; var min = Int.MAX_VALUE
        return m.sumOf { it.sumOf { v ->
            if (v < 0) cnt++
            min = min(min, abs(v)); abs(v).toLong()
        }} - (cnt%2)*2*min
    }

// 0ms
    pub fn max_matrix_sum(m: Vec<Vec<i32>>) -> i64 {
        let (mut c, mut min) = (0, i64::MAX);
        m.iter().map(|r| r.iter().map(|&x|{ let v = x.abs() as i64;
            min = min.min(v); c += (x < 0) as i64; v
        }).sum::<i64>()).sum::<i64>() - 2*min*(c&1)
    }