Update stack_queue.md

Author: skyz8421

data_structure/stack_queue.md

@@ -302,7 +302,35 @@ class Solution:
 
 ```
 
-或者考虑使用双边队列
+或者考虑构建一个单调队列，自定义其pop，push等操作。
+```python
+from collections import deque
+class MonoQueue:
+    def __init__(self):
+        self.dq = deque()
+    def pop(self, val):
+        if self.dq and self.dq[0] == val:
+            self.dq.popleft()
+    def push(self, val):
+        while self.dq and self.dq[-1] < val:
+            self.dq.pop()
+        self.dq.append(val)
+
+    def front(self):
+        return self.dq[0]
+
+class Solution:
+    def maxSlidingWindow(self, nums: List[int], k: int) -> List[int]: #最大堆队列
+        mq = MonoQueue()
+        ans = list()
+        for i, num in enumerate(nums):
+            mq.push(num)
+            if i >= k - 1:
+                ans.append(mq.front())
+                mq.pop(nums[i-k+1])
+        return ans
+
+```