239. Sliding Window Maximum

You are given an array of integers nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position. Return the max sliding window.

Example 1: Input: nums = [1,3,-1,-3,5,3,6,7], k = 3 Output: [3,3,5,5,6,7] Explanation: 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 Example 2: Input: nums = [1], k = 1 Output: [1]

Constraints:

1 <= nums.length <= 105
-104 <= nums[i] <= 104
1 <= k <= nums.length

  • code
class Solution:
    def maxSlidingWindow(self, nums: 'List[int]', k: 'int') -> 'List[int]':
        q = deque()        

        def clean(i):
            if q and i - q[0] == k:
                q.popleft()
            while q and nums[i] > nums[q[-1]]: # maintain a strictly descending q
                q.pop()
                
        for i in range(k):
            clean(i)
            q.append(i)
        res = [nums[q[0]]]
        
        for i in range(k, len(nums)):
            clean(i)
            q.append(i)
            res.append(nums[q[0]])
                
        return res