三个月算法进阶--day50

class CQueue:

    def __init__(self):
        self.stack1 = []
        self.stack2 = []

    def appendTail(self, value: int) -> None:
        self.stack1.append(value)

    def deleteHead(self) -> int:
        if not self.stack2:
            while self.stack1:
                self.stack2.append(self.stack1.pop())
        if not self.stack2:
            return -1
        return self.stack2.pop()

class Solution:
    def fib(self, n: int) -> int:
        a, b = 0, 1
        for _ in range(n):
            a, b = b, a + b
        return a