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Queue.py
65 lines (52 loc) · 1.37 KB
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Queue.py
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from Node import Node
class Queue:
def __init__(self):
self._first = None
self._last = None
self._len = 0
def __bool__(self):
return self._first is not None
def enqueue(self, val):
node = Node(val, None)
if self:
prev_last = self._last
self._last = node
prev_last.ref_next = self._last
else:
self._first = node
self._last = node
self._len += 1
def dequeue(self):
if self:
val = self._first.item
self._first = self._first.ref_next
self._len -= 1
if self._len == 0:
self._last = None
return val
else:
raise Exception('Trying to dequeue from an empty Queue')
def peek(self):
if self:
return self._first.item
else:
raise Exception('Trying to peek into an empty Queue')
def __len__(self):
return self._len
def __iter__(self):
curr = self._first
while curr:
val, curr = curr.item, curr.ref_next
yield val
def __str__(self):
return ' '.join(str(val) for val in tuple(self))
def main():
q = Queue()
q.enqueue(3)
q.enqueue(4)
print(q.dequeue())
print(tuple(q))
if q:
print(q)
if __name__ == "__main__":
main()