239. Sliding Window Maximum.cpp

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

        for(int i=0;i<nums.size();i++){
            while(!q.empty() && nums[q.back()] <= nums[i]){
                q.pop_back();
            }
            q.push_back(i);

            if(q.front() == i-k){
                q.pop_front();
            }

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

        return ans;
    }
};