Leetcode 1767 Solution

This article provides solution to leetcode question 1767 (design-front-middle-back-queue)
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https://leetcode.com/problems/design-front-middle-back-queue

Solution

class FrontMiddleBackQueue:

    def __init__(self):
        self.q1 = deque()
        self.q2 = deque()

    def balance(self):
        while len(self.q1) > len(self.q2):
            self.q2.appendleft(self.q1.pop())

        while len(self.q1) + 1 < len(self.q2):
            self.q1.append(self.q2.popleft())

    def pushFront(self, val: int) -> None:
        self.q1.appendleft(val)
        self.balance()

    def pushMiddle(self, val: int) -> None:
        self.q1.append(val)
        self.balance()

    def pushBack(self, val: int) -> None:
        self.q2.append(val)
        self.balance()

    def popFront(self) -> int:
        ans = None

        if len(self.q1):
            ans = self.q1.popleft()
        elif len(self.q2):
            ans = self.q2.popleft()
        else:
            ans = -1

        self.balance()
        return ans

    def popMiddle(self) -> int:
        ans = None

        if len(self.q2) == 0:
            ans = -1
        elif len(self.q1) == len(self.q2):
            ans = self.q1.pop()
        else:
            ans = self.q2.popleft()

        self.balance()
        return ans

    def popBack(self) -> int:
        ans = None

        if len(self.q2):
            ans = self.q2.pop()
        else:
            ans = -1

        self.balance()
        return ans


# Your FrontMiddleBackQueue object will be instantiated and called as such:
# obj = FrontMiddleBackQueue()
# obj.pushFront(val)
# obj.pushMiddle(val)
# obj.pushBack(val)
# param_4 = obj.popFront()
# param_5 = obj.popMiddle()
# param_6 = obj.popBack()