Add AdjacencyMatrix implementation for graphs (#81)

Author: czgdp1807

pydatastructs/graphs/adjacency_matrix.py

@@ -0,0 +1,58 @@
+from pydatastructs.graphs.graph import Graph
+from pydatastructs.linear_data_structures import OneDimensionalArray
+from pydatastructs.utils.misc_util import AdjacencyMatrixGraphNode
+
+__all__ = [
+    'AdjacencyMatrix'
+]
+
+class AdjacencyMatrix(Graph):
+    """
+    Adjacency matrix implementation of graphs.
+
+    See also
+    ========
+
+    pydatastructs.graphs.graph.Graph
+    """
+    def __new__(cls, *vertices):
+        obj = object.__new__(cls)
+        num_vertices = len(vertices)
+        obj.vertices = OneDimensionalArray(
+                        AdjacencyMatrixGraphNode,
+                        num_vertices)
+        for vertex in vertices:
+            obj.vertices[vertex.name] = vertex
+        obj.matrix = OneDimensionalArray(
+                        OneDimensionalArray,
+                        num_vertices)
+        for i in range(num_vertices):
+            obj.matrix[i] = OneDimensionalArray(
+                            bool,
+                            num_vertices)
+            obj.matrix[i].fill(False)
+        return obj
+
+    def is_adjacent(self, node1, node2):
+        return self.matrix[node1][node2]
+
+    def neighbors(self, node):
+        neighbors = []
+        for i in range(self.matrix[node]._size):
+            if self.matrix[node][i]:
+                neighbors.append(self.vertices[i])
+        return neighbors
+
+    def add_vertex(self, node):
+        raise NotImplementedError("Currently we allow "
+                "adjacency matrix for static graphs only")
+
+    def remove_vertex(self, node):
+        raise NotImplementedError("Currently we allow "
+                "adjacency matrix for static graphs only.")
+
+    def add_edge(self, source, target):
+        self.matrix[source][target] = True
+
+    def remove_edge(self, source, target):
+        self.matrix[source][target] = False

pydatastructs/graphs/graph.py

@@ -13,7 +13,7 @@ class Graph(object):
     implementation: str
         The implementation to be used for storing
         graph in memory.
-        By default, 'adjacency_list'
+        By default, 'adjacency_list'.
     vertices: AdjacencyListGraphNode(s)
         For AdjacencyList implementation vertices
         can be passed for initializing the graph.
@@ -48,6 +48,9 @@ def __new__(cls, *args, **kwargs):
         if implementation is 'adjacency_list':
             from pydatastructs.graphs.adjacency_list import AdjacencyList
             return AdjacencyList(*args)
+        elif implementation is 'adjacency_matrix':
+            from pydatastructs.graphs.adjacency_matrix import AdjacencyMatrix
+            return AdjacencyMatrix(*args)
         else:
             raise NotImplementedError("%s implementation is not a part "
                                       "of the library currently."%(implementation))

pydatastructs/graphs/tests/test_adjacency_matrix.py

@@ -0,0 +1,21 @@
+from pydatastructs.graphs import Graph
+from pydatastructs.utils import AdjacencyMatrixGraphNode
+
+def test_AdjacencyMatrix():
+    v_0 = AdjacencyMatrixGraphNode(0, 0)
+    v_1 = AdjacencyMatrixGraphNode(1, 1)
+    v_2 = AdjacencyMatrixGraphNode(2, 2)
+    g = Graph(v_0, v_1, v_2, implementation='adjacency_matrix')
+    g.add_edge(0, 1)
+    g.add_edge(1, 2)
+    g.add_edge(2, 0)
+    assert g.is_adjacent(0, 1) is True
+    assert g.is_adjacent(1, 2) is True
+    assert g.is_adjacent(2, 0) is True
+    assert g.is_adjacent(1, 0) is False
+    assert g.is_adjacent(2, 1) is False
+    assert g.is_adjacent(0, 2) is False
+    neighbors = g.neighbors(0)
+    assert neighbors == [v_1]
+    g.remove_edge(0, 1)
+    assert g.is_adjacent(0, 1) is False

pydatastructs/utils/misc_util.py

@@ -190,17 +190,17 @@ class AdjacencyMatrixGraphNode(GraphNode):
     Parameters
     ==========
 
-    name: str
-        The name of the node by which it is identified
-        in the graph. Must be unique.
+    name: int
+        The index of the node in the AdjacencyMatrix.
     data
         The data to be stored at each graph node.
     """
     __slots__ = ['name', 'data']
 
     def __new__(cls, name, data):
         obj = GraphNode.__new__(cls)
-        obj.name, obj.data = name, data
+        obj.name, obj.data, obj.is_connected = \
+            name, data, None
         return obj
 
 class GraphEdge(object):

pydatastructs/utils/tests/test_misc_util.py

@@ -17,8 +17,8 @@ def test_AdjacencyListGraphNode():
     assert str(g) == "('g', 0)"
 
 def test_AdjacencyMatrixGraphNode():
-    g = AdjacencyMatrixGraphNode('g', 3)
-    assert str(g) == "('g', 3)"
+    g = AdjacencyMatrixGraphNode(1, 3)
+    assert str(g) == "(1, 3)"
 
 def test_GraphEdge():
     g_1 = AdjacencyListGraphNode('g_1', 1)