Length of longest subarray with at most k frequency

Array Hash Table Sliding Window

56.4% acceptance

Feb 25, 2026

1179

You are given an integer array nums and an integer k. The frequency of an element x is the number of times it occurs in an array. An array is called good if the frequency of each element in this array is less than or equal to k. Return the length of the longest good subarray of nums.

Solution

Rust

Time O(n²)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn max_subarray_length(nums: Vec<i32>, k: i32) -> i32 {
    use std::collections::HashMap;
    let mut freq: HashMap<i32, i32> = HashMap::new();
    let mut left = 0usize;
    let mut ans = 0i32;
    for right in 0..nums.len() {
      let e = freq.entry(nums[right]).or_insert(0);
      *e += 1;
      while *freq.get(&nums[right]).unwrap() > k {
        *freq.get_mut(&nums[left]).unwrap() -= 1;
        left += 1;
      }
      ans = ans.max((right - left + 1) as i32);
    }
    ans
  }
}