class SplayedHashBucket(collections.MutableMapping):
'''
A hash bucket is used to hold objects that hash to the same value in a hash table.
This is hash bucket using a splay tree. This masquerades as a python dict in code
where it is used. Since splat tree is used lookups on avg take Olog(n)
Note: HASHBUCKET ITERATION YIELDS KEYS. not the key value pairs in the bucket.
'''
def __init__(self):
self._st = SplayTree()
def __len__(self):
return self._st.node_count
def get(self, key, default = None):
'''
Get object associated with a key and on key miss return specified default. This is
there in Python dict and this class masquerades as dict, we implement it.
'''
try:
value = self[key]
return value
except KeyError:
return default
def __getitem__(self, key):
value = self._st.find(key)
if value == None:
raise KeyError('Key Error: %s ' % repr(key))
return value
def __delitem__(self, key):
if key in self._st:
self._st.remove(key)
else:
raise KeyError('Key Error: %s ' % repr(key))
def __setitem__(self, key, obj):
if key in self._st:
self._st.replace(key, obj)
else:
self._st.insert(key, obj)
def __iter__(self):
for key, value in self._st.inorder_traversal_with_stack():
yield key
traversed.append((key, value))
print('Tree inorder traversal (key, value) pairs:')
print(traversed)
if __name__ == '__main__':
bst = SplayTree()
print('Node count is %s' % str(bst.node_count))
print('Adding key value pairs (1, 1), (2, 2), .... (6, 6)')
kvpairs = [(5, 5), (2, 2), (7, 7), (1, 1), (3, 3), (9, 9), (8, 8), (4, 4),
(6, 6)]
for kvpair in kvpairs:
bst.insert(key=kvpair[0], obj=kvpair[1])
print_tree_inorder(bst)
print_tree_preorder(bst)
print_tree_postorder(bst)
#remove
element_to_remove = 9
print('removing element %s' % str(element_to_remove))
bst.remove(key=element_to_remove)
print_tree_inorder_using_stack(bst)
#replace obj for a key
key_to_replace = 1
new_object_for_Key = 111
bst.replace(key=key_to_replace, obj=new_object_for_Key)
print_tree_inorder_using_stack(bst)
