LeetCode Entry

1878. Get Biggest Three Rhombus Sums in a Grid

16.03.2026 medium 2026 kotlin rust

Top 3 rhombus sums

1878. Get Biggest Three Rhombus Sums in a Grid medium blog post substack youtube

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Problem TLDR

Top 3 rhombus sums #medium

Intuition

Brute-force.

Approach

• the distance from center to top is the exact number of steps from top to right

Complexity

• Time complexity: \(O((mn)^2)\)

• Space complexity: \(O((mn)^2)\), can be O(1)

Code

// 245ms
    fun getBiggestThree(g: Array<IntArray>) = buildSet {
        for (y in g.indices)  for (x in g[0].indices) {
            add(g[y][x])
            for (d in 1..minOf(x, g[0].size-1-x, y, g.size-1-y)) {
                var c = 0; var i = y-d; var j = x
                for ((dy, dx) in listOf(1 to 1, 1 to -1, -1 to -1, -1 to 1))
                    repeat(d) { c += g[i][j]; i += dy; j += dx }
                add(c)
            }
        }
    }.sortedDescending().take(3)

// 13ms
    pub fn get_biggest_three(g: Vec<Vec<i32>>) -> Vec<i32> {
        let (mut s, m, n) = (vec![], g.len(), g[0].len());
        for y in 0..m { for x in 0..n { s.push(g[y][x]);
            for d in 1..=x.min(n-1-x).min(y).min(m-1-y) {
                let (mut c, mut i, mut j) = (0, y-d, x);
                for (dx,dy) in [(1,1),(1,!0),(!0,!0),(!0,1)] { for _ in 0..d
                    { c+=g[i][j]; i=i.wrapping_add(dx); j=j.wrapping_add(dy) }
                }
                s.push(c)
            }
        }} s.sort_unstable_by_key(|&x|-x); s.dedup(); s.truncate(3); s
    }