相关题目
225. 用队列实现栈:弹出元素时,将对首的元素出列加到队尾,直到只剩下初始队列时队尾一个元素为止,然后弹出这个元素,即可实现LIFO
232. 用栈实现队列:用两个栈实现队列的功能,出栈时,将栈1的元素全部弹出压到栈2中,然后弹出栈2栈顶的元素,即可实现FIFO
# 225. 用队列实现栈
class MyStack:def __init__(self):self.queue = []def push(self, x: int) -> None:self.queue.append(x)def pop(self) -> int:n = len(self.queue)while n > 1:self.queue.append(self.queue.pop(0))n -= 1return self.queue.pop(0)def top(self) -> int:return self.queue[-1]def empty(self) -> bool:return len(self.queue) == 0
# 232. 用栈实现队列
class MyQueue:def __init__(self):self.stk1 = []self.stk2 = []def push(self, x: int) -> None:self.stk1.append(x)def pop(self) -> int:# 先调⽤ peek 保证 s2 ⾮空self.peek()return self.stk2.pop()def peek(self) -> int:if not self.stk2:while self.stk1:self.stk2.append(self.stk1.pop())return self.stk2[-1]def empty(self) -> bool:return len(self.stk2) == 0 and len(self.stk1) == 0