/
deque.py
88 lines (64 loc) · 1.66 KB
/
deque.py
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class Node:
def __init__(self, x):
self.val = x
self.next = None
self.prev = None
class Deque:
def __init__(self):
self.head = None
self.tail = None
self.cnt = 0
def pushFront(self, x):
node = Node(x)
if self.cnt == 0:
self.head = node
self.tail = self.head
else:
node.next = self.head
self.head.prev = node
self.head = node
self.cnt += 1
def pushBack(self, x):
node = Node(x)
if self.cnt == 0:
self.head = node
self.tail = self.head
else:
self.tail.next = node
node.prev = self.tail
self.tail = self.tail.next
self.cnt += 1
def popFront(self):
if self.cnt == 0:
return
elif self.cnt == 1:
self.head = None
self.tail = None
else:
self.head = self.head.next
self.head.prev.next = None
self.head.prev = None
self.cnt -= 1
def popBack(self):
if self.cnt == 0:
return
elif self.cnt == 1:
self.head = None
self.tail = None
else:
self.tail = self.tail.prev
self.tail.next.prev = None
self.tail.next = None
self.cnt -= 1
def peekFront(self):
if self.head is None:
return
return self.head.val
def peekBack(self):
if self.tail is None:
return
return self.tail.val
def size(self):
return self.cnt
def empty(self):
return self.cnt == 0