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arraydeque.py
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arraydeque.py
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'''
An array-based list implementation with O(1+min{i,n-i}) amortized update time.
Stores the list in an array, a, so that the i'th list item is stored
at a[(j+i)%len(a)].
Uses a doubling strategy for resizing a when it becomes full or too empty.
'''
from utils import new_array
from base import BaseList
class ArrayDeque(BaseList):
def __init__(self, iterable=[]):
self._initialize()
self.add_all(iterable)
def _initialize(self):
self.a = new_array(1)
self.j = 0
self.n = 0
def get(self, i):
if i < 0 or i >= self.n: raise IndexError()
return self.a[(i+self.j)%len(self.a)]
def set(self, i, x):
if i < 0 or i >= self.n: raise IndexError()
y = self.a[(i+self.j)%len(self.a)]
self.a[(i+self.j)%len(self.a)] = x
return y
def add(self, i, x):
if i < 0 or i > self.n: raise IndexError()
if self.n == len(self.a): self._resize()
if i < self.n/2:
self.j = (self.j-1) % len(self.a)
for k in range(i):
self.a[(self.j+k)%len(self.a)] = self.a[(self.j+k+1)%len(self.a)]
else:
for k in range(self.n, i, -1):
self.a[(self.j+k)%len(self.a)] = self.a[(self.j+k-1)%len(self.a)]
self.a[(self.j+i)%len(self.a)] = x
self.n += 1
def remove(self, i):
if i < 0 or i >= self.n: raise IndexError()
x = self.a[(self.j+i)%len(self.a)]
if i < self.n / 2:
for k in range(i, 0, -1):
self.a[(self.j+k)%len(self.a)] = self.a[(self.j+k-1)%len(self.a)]
self.j = (self.j+1) % len(self.a)
else:
for k in range(i, self.n-1):
self.a[(self.j+k)%len(self.a)] = self.a[(self.j+k+1)%len(self.a)]
self.n -= 1
if len(self.a) >= 3*self.n: self._resize()
return x
def _resize(self):
b = new_array(max(1, 2*self.n))
for k in range(self.n):
b[k] = self.a[(self.j+k)%len(self.a)]
self.a = b
self.j = 0