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implement-stack-using-queues_225.py
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implement-stack-using-queues_225.py
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# Implement a last-in-first-out (LIFO) stack using only two queues. The implemented stack should support all the functions of a normal stack (push, top, pop, and empty).
# Implement the MyStack class:
# void push(int x) Pushes element x to the top of the stack.
# int pop() Removes the element on the top of the stack and returns it.
# int top() Returns the element on the top of the stack.
# boolean empty() Returns true if the stack is empty, false otherwise.
# Notes:
# You must use only standard operations of a queue, which means that only push to back, peek/pop from front, size and is empty operations are valid.
# Depending on your language, the queue may not be supported natively. You may simulate a queue using a list or deque (double-ended queue) as long as you use only a queue's standard operations.
# Example 1:
# Input
# ["MyStack", "push", "push", "top", "pop", "empty"]
# [[], [1], [2], [], [], []]
# Output
# [null, null, null, 2, 2, false]
# Explanation
# MyStack myStack = new MyStack();
# myStack.push(1);
# myStack.push(2);
# myStack.top(); // return 2
# myStack.pop(); // return 2
# myStack.empty(); // return False
# ---------------------------------------Runtime 38 ms Beats 71.22% Memory 16.4 MB Beats 32.19%---------------------------------------
class MyStack:
def __init__(self):
self.stack = []
def push(self, x: int) -> None:
self.stack.append(x)
def pop(self) -> int:
return self.stack.pop()
def top(self) -> int:
return self.stack[-1]
def empty(self) -> bool:
return len(self.stack) == 0