Update 0225._implement_stack_using_queues.md

docs/Leetcode_Solutions/Python/0225._implement_stack_using_queues.md

-###225. Implement Stack using Queues
-
-题目:
-
-<https://leetcode.com/problems/implement-stack-using-queues/>
-
-
-难度:
-
-Easy
-
-
-又到了作弊神预言Python的强项
-
-
+# 225. Implement Stack using Queues
+
+**<font color=green>难度: Easy</font>**
+
+## 刷题内容
+
+> 原题连接
+
+* https://leetcode.com/problems/implement-stack-using-queues/
+
+> 内容描述
+
 ```
-class Stack(object):
-    def __init__(self):
-        """
-        initialize your data structure here.
-        """
-        self.lst = []
-        
-
-    def push(self, x):
-        """
-        :type x: int
-        :rtype: nothing
-        """
-        self.lst.append(x)
-        
-
-    def pop(self):
-        """
-        :rtype: nothing
-        """
-        self.lst.remove(self.lst[-1])
-        
-
-    def top(self):
-        """
-        :rtype: int
-        """
-        return self.lst[-1]
-
-    def empty(self):
-        """
-        :rtype: bool
-        """
-        return self.lst == []
-        
-```
-
+
+Implement the following operations of a stack using queues.
+
+push(x) -- Push element x onto stack.
+pop() -- Removes the element on top of the stack.
+top() -- Get the top element.
+empty() -- Return whether the stack is empty.
+Example:
+
+MyStack stack = new MyStack();
+
+stack.push(1);
+stack.push(2);  
+stack.top();   // returns 2
+stack.pop();   // returns 2
+stack.empty(); // returns false
+Notes:
+
+You must use only standard operations of a queue -- which means only push to back, peek/pop from front, size, and is empty operations are valid.
+Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue.
+You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).
+```
+
+## 解题方案
+
+> 思路 1
+******- 时间复杂度: Push O(N) + Pop O(1) ******- 空间复杂度: O(N)******
+
+
+
+```python
+class MyStack:
+
+    def __init__(self):
+        """
+        Initialize your data structure here.
+        """
+        self.queue = collections.deque()
+        
+    def push(self, x: int) -> None:
+        """
+        Push element x onto stack.
+        """
+        self.queue.append(x)
+        for _ in range(len(self.queue) - 1):
+            self.queue.append(self.queue.popleft())
+        
+    def pop(self) -> int:
+        """
+        Removes the element on top of the stack and returns that element.
+        """
+        return self.queue.popleft()
+
+    def top(self) -> int:
+        """
+        Get the top element.
+        """
+        return self.queue[0]
+        
+    def empty(self) -> bool:
+        """
+        Returns whether the stack is empty.
+        """
+        return not len(self.queue)
+```
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