Learning-Data-Structures-and-Algorithm-Python/implement_queue_using_stack.py at master · AnushreeBagchi/Learning-Data-Structures-and-Algorithm-Python · GitHub

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class Stack:
    def __init__(self):
        self.items = []
    def size(self):
        return len(self.items)
    def push(self, value):
        self.items.append(value)
    def pop(self):
        if self.size == 0:
            return None
        return self.items.pop()

class Queue:
    def __init__(self):
        self.instorage = Stack()
        self.outstorage = Stack()

    def size(self):
        return self.instorage.size() + self.outstorage.size()
    def enqueue(self, value):
        self.instorage.push(value)
    def dequeue(self):
        if not self.outstorage.items:
            while self.instorage.items:
                self.outstorage.push(self.instorage.pop())
            return self.outstorage.pop()

q = Queue()
q.enqueue(1)
q.enqueue(2)
q.enqueue(3)

# Test size
print ("Pass" if (q.size() == 3) else "Fail")

# Test dequeue
print ("Pass" if (q.dequeue() == 1) else "Fail")

# Test enqueue
q.enqueue(4)
print ("Pass" if (q.dequeue() == 2) else "Fail")
print ("Pass" if (q.dequeue() == 3) else "Fail")
print ("Pass" if (q.dequeue() == 4) else "Fail")
q.enqueue(5)
print ("Pass" if (q.size() == 1) else "Fail")