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## Problem

Implement the following operations of a queue using stacks.

push(x) – Push element x to the back of queue. pop() – Removes the element from in front of queue. peek() – Get the front element. empty() – Return whether the queue is empty. Example:

MyQueue queue = new MyQueue();

queue.push(1);
queue.push(2);
queue.peek();  // returns 1
queue.pop();   // returns 1
queue.empty(); // returns false


Notes:

You must use only standard operations of a stack – which means only push to top, peek/pop from top, size, and is empty operations are valid. Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack. You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).

## Code

class MyQueue:

def __init__(self):
"""
"""
self.stack = []

def push(self, x: int) -> None:
"""
Push element x to the back of queue.
"""
temp_stack = []
while self.stack:
temp_stack.append(self.stack.pop())

self.stack.append(x)
while temp_stack:
self.stack.append(temp_stack.pop())

def pop(self) -> int:
"""
Removes the element from in front of queue and returns that element.
"""
return self.stack.pop()

def peek(self) -> int:
"""
Get the front element.
"""
return self.stack[-1]

def empty(self) -> bool:
"""
Returns whether the queue is empty.
"""
return not self.stack

# Your MyQueue object will be instantiated and called as such:
# obj = MyQueue()
# obj.push(x)
# param_2 = obj.pop()
# param_3 = obj.peek()
# param_4 = obj.empty()

class MyQueue:

def __init__(self):
"""
"""
self.stack_input = []
self.stack_output = []

def push(self, x: int) -> None:
"""
Push element x to the back of queue.
"""
self.stack_input.append(x)

def pop(self) -> int:
"""
Removes the element from in front of queue and returns that element.
"""
self.peek()
return self.stack_output.pop()

def peek(self) -> int:
"""
Get the front element.
"""
if not self.stack_output:
while self.stack_input:
self.stack_output.append(self.stack_input.pop())

return self.stack_output[-1]

def empty(self) -> bool:
"""
Returns whether the queue is empty.
"""
return not self.stack_output and not self.stack_input

# Your MyQueue object will be instantiated and called as such:
# obj = MyQueue()
# obj.push(x)
# param_2 = obj.pop()
# param_3 = obj.peek()
# param_4 = obj.empty()