2958.MaxSubarrayLength.cs

// 2958. Length of Longest Subarray With at Most K Frequency
// 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.
// A subarray is a contiguous non-empty sequence of elements within an array.

// Example 1:
// Input: nums = [1,2,3,1,2,3,1,2], k = 2
// Output: 6
// Explanation: The longest possible good subarray is [1,2,3,1,2,3] since the values 1, 2, and 3 occur at most twice in this subarray. Note that the subarrays [2,3,1,2,3,1] and [3,1,2,3,1,2] are also good.
// It can be shown that there are no good subarrays with length more than 6.
// Example 2:
// Input: nums = [1,2,1,2,1,2,1,2], k = 1
// Output: 2
// Explanation: The longest possible good subarray is [1,2] since the values 1 and 2 occur at most once in this subarray. Note that the subarray [2,1] is also good.
// It can be shown that there are no good subarrays with length more than 2.
// Example 3:
// Input: nums = [5,5,5,5,5,5,5], k = 4
// Output: 4
// Explanation: The longest possible good subarray is [5,5,5,5] since the value 5 occurs 4 times in this subarray.
// It can be shown that there are no good subarrays with length more than 4.
 
// Constraints:
// 1 <= nums.length <= 105
// 1 <= nums[i] <= 109
// 1 <= k <= nums.length

public class Solution {
    public int MaxSubarrayLength(int[] nums, int k) {
        Dictionary<int,int> freq = new();
        int j = 0;
        int result = 0;
        for(int i = 0; i < nums.Length; i++){
            if(freq.ContainsKey(nums[i])){
                while(j < i && freq[nums[i]] > k-1){
                    freq[nums[j]]--;
                    j++;
                }
                freq[nums[i]]++;
            }
            else{
                freq[nums[i]] = 1;
            }
            result = Math.Max(result, i-j+1);
        }
        return result;
    }
}