LeetCode Entry

3354. Make Array Elements Equal to Zero

28.10.2025 easy 2025 kotlin rust

Places & directions that lead the simulation to all zeros

3354. Make Array Elements Equal to Zero easy blog post substack youtube

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Problem TLDR

Places & directions that lead the simulation to all zeros #easy #simualtion

Intuition

Try every combination of place and direction

Approach

• without simulation: sum diff (left, right) must be less than 2

Complexity

• Time complexity: \(O(n^3)\), n^2 for the simulation

• Space complexity: \(O(n)\)

Code

// 261ms
    fun countValidSelections(n: IntArray) =
        n.indices.sumOf { s -> if (n[s] == 0) listOf(-1,1).count { d ->
            val n = n.clone(); var c = s; var d = d
            while (c in 0..<n.size)
                if (n[c] > 0) { n[c]--; d *= -1; c += d } else c += d
            n.all { it == 0 }
        } else 0 }

// 2ms
    pub fn count_valid_selections(n: Vec<i32>) -> i32 {
        let (mut r, mut l, mut res) = (n.iter().sum::<i32>(),0,0);
        for n in n {
            l += n; r -= n;
            if n < 1 {
                if (l - r).abs() < 2 { res += 1 }
                if l == r { res += 1 }
            }
        } res
    }