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deque.py
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deque.py
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class Deque:
"""implement deque using array
a deque of at most n elements using an array of n+1 element size
"""
def __init__(self, length):
self.length = length
self.deque = [None]*(length+1)
self.head = 0
self.tail = 0
def head_enqueue(self, x):
if self.is_full():
return 'Overflow'
if self.head == 0:
self.head = self.length
else:
self.head = self.head - 1
self.deque[self.head] = x
def head_dequeue(self):
if self.is_empty():
return 'Underflow'
x = self.deque[self.head]
if self.head == self.length:
self.head = 0
else:
self.head = self.head + 1
return x
def tail_enqueue(self, x):
if self.is_full():
return 'Overflow'
self.deque[self.tail] = x
if self.tail == self.length:
self.tail = 0
else:
self.tail = self.tail + 1
def tail_dequeue(self):
if self.is_empty():
return 'Underflow'
if self.tail == 0:
self.tail = self.length
else:
self.tail = self.tail - 1
return self.deque[self.tail]
def is_empty(self):
return self.head == self.tail
def is_full(self):
return self.head == self.tail+1 or (self.head == 0 and self.tail == self.length)
if __name__ == "__main__":
deque = Deque(3)
deque.tail_enqueue(2)
deque.tail_enqueue(3)
deque.head_enqueue(1)
print(deque.deque)
print(deque.head_enqueue('string')) # output:'Overflow'
print(deque.head_dequeue()) # output:1
print(deque.tail_dequeue()) # output:3
print(deque.head_dequeue()) # output:2
print(deque.head_dequeue()) # output:'Underflow'