Update 239.sliding-window-maximum.md

Author: azl397985856

problems/239.sliding-window-maximum.md

@@ -162,18 +162,14 @@ Python3:
 ```python
 class Solution:
     def maxSlidingWindow(self, nums: List[int], k: int) -> List[int]:
-        deque, res, n = collections.deque(), [], len(nums)
-        for i in range(n):
-            # 移除前面实现的元素，整因为如此，才需要双端队列
-            while deque and deque[0] < i - k + 1:
-                deque.popleft()
-            # 下面三行，类似单调递增栈
-            while deque and nums[i] > nums[deque[-1]]:
-                deque.pop()
-            deque.append(i)
-            if i >= k - 1:
-                res.append(nums[deque[0]])
-        return res
+        q = collections.deque() # 本质就是单调队列
+        ans = []
+        for i in range(len(nums)):
+            while q and nums[q[-1]] <= nums[i]: q.pop() # 维持单调性
+            while q and i - q[0] >= k: q.popleft() # 移除失效元素
+            q.append(i)
+            if i >= k - 1: ans.append(nums[q[0]])
+        return ans
 ```
 
 **复杂度分析**