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class Solution {
public:
    vector<int> maxSlidingWindow(vector<int>& nums, int k) {
        vector<int> ans;
        deque<int> q;

        for(int i=0; i<nums.size(); i++){
            while(!q.empty() && q.front() < i-k+1)
                q.pop_front();

            while(!q.empty() && nums[q.back()] < nums[i])
                q.pop_back();

            q.push_back(i);

            if(i >= k-1)
                ans.push_back(nums[q.front()]);
        }

        return ans;
    }
};