problem:2958. 最多 K 个重复元素的最长子数组

思路：维护滑动窗口的窗口内各个元素至多出现k次即可。nums[i]<=$10^9$，要离散化一下。

Accode:

class Solution {
public:
    int maxSubarrayLength(vector<int>& nums, int k) {
        unordered_map<int,int> dict;
        int len = nums.size();
        int sum = 0, ans = 0;
        int left = 0;
        for (int i = 0; i < len; i++) {
            dict[nums[i]]++;
            sum += 1;
            if (dict[nums[i]] > k) {
                for (int j = left; j < i; j++) {
                    dict[nums[j]]--;
                    sum -= 1;
                    if (dict[nums[i]] <= k) {
                        left = j + 1;
                        break;
                    }
                }
            }
            ans = max(ans, sum);
        }
        return ans;
    }
}
;

时间复杂度：$o(n)$