class TestStringMethods(unittest.TestCase):
def setUp(self):
self.array = [1, 2, 3, 4, 5, 10, 20, 30, 100, 200]
self.u = 256
self.trie = XFastTrie(self.array, self.u)
def test_find(self):
for i in xrange(self.u):
expected = i in self.array
self.assertEqual(self.trie.find(i), expected)
def test_predecessor(self):
for i in xrange(self.u):
correct = None
for value in self.array:
if value < i:
correct = value
else:
break
self.assertEqual(self.trie.predecessor(i), correct)
def test_successor(self):
for i in xrange(self.u):
correct = None
if i < self.array[-1]:
for value in self.array:
if value > i:
correct = value
break
self.assertEqual(self.trie.successor(i), correct)
class YFastTrie:
# assumes that values is a sorted array
def __init__(self, values, u):
self.x_trie = None
self.search_trees = {}
def chunk_array(l):
count = len(l)
n = int(math.ceil(math.log(count, 2)))
for i in range(0, count, n):
yield l[i:i + n]
chunks = list(chunk_array(values))
reps = []
for chunk in chunks:
rep = chunk[0] + chunk[-1] - chunk[0]
reps.append(rep)
search_tree = SearchTree(chunk)
self.search_trees[rep] = search_tree
self.x_trie = XFastTrie(reps, u)
def find(self, x):
def find_tree(node, x):
if node is None:
return False
if node.value == x:
return True
elif x > node.value:
return find_tree(node.right_ptr, x)
elif x < node.value:
return find_tree(node.left_ptr, x)
reps = self._find_reps(x)
for rep in reps:
if rep is None:
continue
tree = self.search_trees[rep]
if find_tree(tree.root, x):
return True
return False
def predecessor(self, x):
def pred_tree(node, x):
predecessor = None
while True:
if node is None:
break
if node.value < x:
predecessor = node.value
if x <= node.value:
node = node.left_ptr
else:
node = node.right_ptr
return predecessor
reps = self._find_reps(x)
best_result = None
for rep in reps:
if rep is None:
continue
tree = self.search_trees[rep]
if tree.min > x:
continue
result = pred_tree(tree.root, x)
if best_result is None or result > best_result:
best_result = result
return best_result
def successor(self, x):
def succ_tree(node, x):
successor = None
while True:
if node is None:
break
if node.value > x:
successor = node.value
if x >= node.value:
node = node.right_ptr
else:
node = node.left_ptr
return successor
reps = self._find_reps(x)
best_result = None
for rep in reps:
if rep is None:
continue
tree = self.search_trees[rep]
if tree.max < x:
continue
result = succ_tree(tree.root, x)
if best_result is None or result < best_result:
best_result = result
return best_result
def _find_reps(self, x):
predecessor = None
successor = self.x_trie.successor(x)
if successor is None:
if self.x_trie.find(x):
successor = x
if successor is not None:
predecessor = self.x_trie.predecessor(successor)
else:
predecessor = self.x_trie.predecessor(x)
return [predecessor, successor]
