LeetCode Entry

2958. Length of Longest Subarray With at Most K Frequency

12.08.2026 medium 2026 kotlin rust

Max subarray freq less than K

2958. Length of Longest Subarray With at Most K Frequency medium substack youtube

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Problem TLDR

Max subarray freq less than K

Intuition

Sliding window: always slide forward, shring while its bad freq. Max window: increase if good, move right if bad

Approach

Kotlin: HashMap merge(x, 1, Int::plus) Rust: HashMap entry and_modify

Complexity

• Time complexity: \(O(n)\)

• Space complexity: \(O(1)\)

Code

    fun maxSubarrayLength(n: IntArray, k: Int)=run {
        val f = HashMap<Int, Int>(); var j = 0; var bad = 0
        for (i in n.indices) {
            if (f.merge(n[i], 1, Int::plus)!! == k + 1) bad++
            if (bad > 0 && f.merge(n[j++], -1, Int::plus) == k) bad--
        }; n.size - j
    }

    pub fn max_subarray_length(n: Vec<i32>, k: i32) -> i32 {
        let (mut f, mut j, mut b) = (HashMap::new(), 0, 0);
        for &x in &n {
            f.entry(x).and_modify(|c| { b += (*c == k) as i32; *c += 1 }).or_insert(1);
            if b > 0 {
                f.entry(n[j]).and_modify(|c| { b -= (*c == k + 1) as i32; *c -= 1 });
                j += 1;
            }
        } (n.len() - j) as i32
    }