problem:2461. 长度为 K 子数组中的最大和

思路:相似题

Accode:

class Solution {
public:
    long long maximumSubarraySum(vector<int>& nums, int k) {
        unordered_map<int, int> dict;
        deque<int> deq;
        int m = k;
        long long sum = 0;
        int len = nums.size();
        long long ans = 0;
        for (int i = 0; i < len; i++) {
            if (deq.size() && i - deq.front() + 1 > k) {
                dict[nums[deq.front()]]--;
                if (dict[nums[deq.front()]] == 0)
                    dict.erase(nums[deq.front()]);
                sum -= nums[deq.front()];
                deq.pop_front();
            }
            deq.push_back(i);
            dict[nums[i]]++;
            sum += nums[i];
            if (i + 1 >= k && dict.size() >= m) {
                ans = max(ans, sum);
            }
        }
        return ans;
    }
};

时间复杂度：$o(n)$