def __init__(self, vertices):
self._st = BinarySearchST() # string -> index
# built symbol table to translate strings into indices
for i in range(len(vertices)):
self._st.put(vertices[i], i)
# built array to translate from indices to strings
self._keys = [None] * self._st.size() # index -> string
for name in self._st.keys():
self._keys[self._st.get(name)] = name
# initialise graph
self._graph = Graph(self._st.size()) # the underlying graph
class SymbolGraph:
"""The SymbolGraph class represents an undirected graph, where the vertex
names are arbitrary strings. By providing mappings between vertex names and
integers, it serves as a wrapper around the Graph data type, which assumes
the vertex names are integers between 0 and V - 1.
"""
def __init__(self, vertices):
self._st = BinarySearchST() # string -> index
# built symbol table to translate strings into indices
for i in range(len(vertices)):
self._st.put(vertices[i], i)
# built array to translate from indices to strings
self._keys = [None] * self._st.size() # index -> string
for name in self._st.keys():
self._keys[self._st.get(name)] = name
# initialise graph
self._graph = Graph(self._st.size()) # the underlying graph
def V(self):
return self._graph._V
def E(self):
return self._graph._E
def size(self):
return self._graph._V
def __len__(self):
return self._graph._V
def contains(self, s):
return self._st.contains(s)
def index_of(self, s):
return self._st.get(s)
def name_of(self, v):
return self._keys[v]
def add_edge(self, u, v):
self._graph.add_edge(self.index_of(u), self.index_of(v))
def adj(self, u):
return [self.name_of(adj) for adj in self._graph.adj(self.index_of(u))]
def degree(self, u):
return self._graph.degree(self.index_of(u))
def graph(self):
return self._graph
def __init__(self, filename, delimiter):
"""Initializes a graph from a file using the specified delimiter. Each
line in the file contains the name of a vertex, followed by a list of
the names of the vertices adjacent to that vertex, separated by the
delimiter.
:param filename: the name of the file
:param delimiter: the delimiter between fields
"""
self._st = BinarySearchST() # string -> index
# First pass builds the index by reading strings to associate
# distinct strings with an index
stream = InStream(filename)
while not stream.isEmpty():
a = stream.readLine().split(delimiter)
for i in range(len(a)):
if not self._st.contains(a[i]):
self._st.put(a[i], self._st.size())
stdio.writef("Done reading %s\n", filename)
# inverted index to get keys in an array
self._keys = [None] * self._st.size() # index -> string
for name in self._st.keys():
self._keys[self._st.get(name)] = name
# second pass builds the graph by connecting first vertex on each
# line to all others
self._graph = Graph(self._st.size()) # the underlying graph
stream = InStream(filename)
while stream.hasNextLine():
a = stream.readLine().split(delimiter)
v = self._st.get(a[0])
for i in range(1, len(a)):
w = self._st.get(a[i])
self._graph.add_edge(v, w)
class SymbolGraph:
"""The SymbolGraph class represents an undirected graph, where the vertex
names are arbitrary strings. By providing mappings between vertex names and
integers, it serves as a wrapper around the Graph data type, which assumes
the vertex names are integers.
between 0 and V - 1.
It also supports initializing a symbol graph from a file.
This implementation uses an ST to map from strings to integers,
an array to map from integers to strings, and a Graph to store
the underlying graph.
The index_of and contains operations take time
proportional to log V, where V is the number of vertices.
The name_of operation takes constant time.
"""
def __init__(self, filename, delimiter):
"""Initializes a graph from a file using the specified delimiter. Each
line in the file contains the name of a vertex, followed by a list of
the names of the vertices adjacent to that vertex, separated by the
delimiter.
:param filename: the name of the file
:param delimiter: the delimiter between fields
"""
self._st = BinarySearchST() # string -> index
# First pass builds the index by reading strings to associate
# distinct strings with an index
stream = InStream(filename)
while not stream.isEmpty():
a = stream.readLine().split(delimiter)
for i in range(len(a)):
if not self._st.contains(a[i]):
self._st.put(a[i], self._st.size())
stdio.writef("Done reading %s\n", filename)
# inverted index to get keys in an array
self._keys = [None] * self._st.size() # index -> string
for name in self._st.keys():
self._keys[self._st.get(name)] = name
# second pass builds the graph by connecting first vertex on each
# line to all others
self._graph = Graph(self._st.size()) # the underlying graph
stream = InStream(filename)
while stream.hasNextLine():
a = stream.readLine().split(delimiter)
v = self._st.get(a[0])
for i in range(1, len(a)):
w = self._st.get(a[i])
self._graph.add_edge(v, w)
def contains(self, s):
"""Does the graph contain the vertex named s?
:param s: the name of a vertex
:return:s true if s is the name of a vertex, and false otherwise
"""
return self._st.contains(s)
def index_of(self, s):
"""Returns the integer associated with the vertex named s.
:param s: the name of a vertex
:returns: the integer (between 0 and V - 1) associated with the vertex named s
"""
return self._st.get(s)
def name_of(self, v):
"""Returns the name of the vertex associated with the integer v.
@param v the integer corresponding to a vertex (between 0 and V - 1)
@throws IllegalArgumentException unless 0 <= v < V
@return the name of the vertex associated with the integer v
"""
self._validateVertex(v)
return self._keys[v]
def graph(self):
return self._graph
def _validateVertex(self, v):
# throw an IllegalArgumentException unless 0 <= v < V
V = self._graph.V()
if v < 0 or v >= V:
raise ValueError("vertex {} is not between 0 and {}".format(v, V - 1))