def __getitem__(self, item: str) -> Skiplist:
"""
Return the associated Skiplist to a key or an empty Skiplist
if there's no mapping in the dictionary
"""
if item in self.dictionary:
value = self.dictionary[item]
self.post_file.seek(value.offset)
return Skiplist(pickle.loads(self.post_file.read(value.size)))
else:
return Skiplist([])
def not_merge(l1: Skiplist, l2: Skiplist) -> Skiplist:
"""
Negated the l1 list given the total list of existing doc ids l2
Note: use the underlying list for performances
*params*
- l1 The first Skiplist
- l2 The list of all of the doc ids
*return*
- The negated Skiplist l1 based on l2
"""
out = []
i1, i2 = iter(l1.list), iter(l2.list)
e1, e2 = next(i1, False), next(i2, False)
while e1 and e2:
if e1 == e2:
e1, e2 = next(i1, False), next(i2, False)
elif e1 < e2:
e1 = next(i1, False)
else:
out.append(e2)
e2 = next(i2, False)
if e2:
out.append(e2)
for e in i2:
out.append(e)
return Skiplist(out)
def or_merge(l1: Skiplist, l2: Skiplist) -> Skiplist:
"""
Merge 2 Skiplists based on the OR boolean operator logic
Note: use the underlying list for performances
*params*
- l1 The first Skiplist
- l2 The second Skiplist
*return*
- The merged Skiplist
"""
out = []
i1, i2 = iter(l1.list), iter(l2.list)
e1, e2 = next(i1, False), next(i2, False)
while e1 and e2:
if e1 == e2:
out.append(e1)
e1, e2 = next(i1, False), next(i2, False)
elif e1 < e2:
out.append(e1)
e1 = next(i1, False)
else:
out.append(e2)
e2 = next(i2, False)
if e1:
out.append(e1)
for e in i1:
out.append(e)
elif e2:
out.append(e2)
for e in i2:
out.append(e)
return Skiplist(out)
def and_not_merge(l1: Skiplist, l2: Skiplist) -> Skiplist:
"""
Merge 2 Skiplists based on the AND NOT logic: l1 AND **NOT** l2
*params*
- l1 The first Skiplist
- l2 The second Skiplist (being *negated*)
*return*
- The merged Skiplist
"""
out = []
i1, i2 = iter(l1.list), iter(l2.list)
e1, e2 = next(i1, False), next(i2, False)
while e1 and e2:
if e1 == e2:
e1, e2 = next(i1, False), next(i2, False)
elif e1 < e2:
out.append(e1)
e1 = next(i1, False)
else:
e2 = next(i2, False)
if e1:
out.append(e1)
for e in i1:
out.append(e)
return Skiplist(out)
def and_merge(l1: Skiplist, l2: Skiplist) -> Skiplist:
"""
Merge 2 Skiplists based on the AND boolean operator logic
using Skip pointers whenever possible
*params*
- l1 The first Skiplist
- l2 The second Skiplist
*return*
- The merged Skiplist
"""
out = []
i1, i2 = iter(l1), iter(l2)
try:
e1, e2 = next(i1, False), next(i2, False)
while e1 and e2:
if e1 == e2:
out.append(e1)
e1, e2 = next(i1, False), next(i2, False)
elif e1 < e2:
e1 = i1.__next__(e2)
else:
e2 = i2.__next__(e1)
except StopIteration:
pass
return Skiplist(out)
def test_remove():
sklist = Skiplist()
sklist.add(1)
sklist.add(2)
assert sklist.remove(1) == True
assert sklist.remove(1) == False
assert sklist.remove(2) == True
def test_find_predecessor():
sklist = Skiplist()
sklist.add(1)
sklist.add(2)
sklist.add(3)
sklist.add(4)
sklist.add(5)
assert sklist.find_predecessor(6)[0].data == 5
assert sklist.find_predecessor(4.5)[0].data == 4
assert sklist.find_predecessor(2.9)[0].data == 2
assert sklist.find_predecessor(1.1)[0].data == 1
assert sklist.find_predecessor(0.9)[0] == None
def test_add():
sklist = Skiplist()
assert sklist.add(10) == True
assert sklist.add(20) == True
assert sklist.add(10) == False
def test_find():
sklist = Skiplist()
sklist.add(1)
sklist.add(2)
sklist.add(3)
assert sklist.find(1) == 1
assert sklist.find(0) == 1
assert sklist.find(2) == 2
assert sklist.find(10) == None
assert sklist.find(1.5) == 2
assert sklist.find(3) == 3
def test_find_predecessor():
sklist = Skiplist()
sklist.add(1)
sklist.add(2)
sklist.add(3)
def __init__(self, limit=100):
Skiplist.__init__(self, limit)
self.stack = list() # a list of tuples