239. Sliding window Maximum *hard*-The maximum value of sliding windows

Given an array nums, there is a sliding window of size K which are moving from the very left of the array To the very right. You can only see the Knumbers in the window. Each of the sliding window moves right by one position.

For example,
Given nums = [1,3,-1,-3,5,3,6,7] , and k = 3.

Window position                Max---------------               -----[1  3  -1]-3  5  3  6  7       3 1 [3  - 1  -3] 5  3  6  7       3 1 3  [-1  -3  5] 3  6  7       5 1  3  -1 [-3  5  3] 6  7       5 1  3  -1  -3 [5  3  6] 7       6 1  3  -1  -3  5 [3  6  7]      7

Therefore, return the max sliding window as [3,3,5,5,6,7] .

Note:
You may assume K are always valid, Ie:1≤k≤input array's size for non-empty array.

Follow up:
Could solve it in linear time?

Hint:

1. How about using a data structure such as deque (double-ended queue)?
2. The queue size need not being the same as the window ' s size.
3. Remove redundant elements and the queue should store only elements that need to be considered.

classSolution { Public: Vector<int> Maxslidingwindow (vector<int>& Nums,intk) {deque<int>DQ; Vector<int>ans; intn =nums.size (), I;  for(i =0; I < n; i++)    {        if(Dq.front () = = i-k) Dq.pop_front ();  while(!dq.empty () && nums[dq.back ()] <Nums[i]) dq.pop_back ();        Dq.push_back (i); if(I >= K-1) Ans.push_back (Nums[dq.front ()); }    returnans; }};

Dual-ended queues

239. Sliding window Maximum *hard*-The maximum value of sliding windows