problem:2841. 几乎唯一子数组的最大和

思路：定长滑动窗口的变形题

Accode:

class Solution {
public:
    long long maxSum(vector<int>& nums, int m, int k) {
        unordered_map<int,int> dict;
        deque<int> deq;
        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：$o(n)$