Merge pull request #38 from master-fury/master

BFS (Graph Algorithm)

Author: senthilkumar1729

Graph_Algorithms/src/Breadth_First_Traversal/BFS.py

@@ -0,0 +1,69 @@
+#BFS by Master-Fury
+import collections
+
+"""
+    Wrapper function for the print function.
+    Used as the default visitFunc for bfs
+"""
+def visitPrint(i):
+    print(i)
+
+"""
+    A class representing a undirected graph of nodes.
+    An edge can be added between two nodes by calling addEdge
+        *This class assumes all edge weights are equal
+"""
+class Graph:
+    def __init__(self):
+        self.adjList = collections.defaultdict(set)
+
+    def addEdge(self, node1, node2):
+        self.adjList[node1].add(node2)
+        self.adjList[node2].add(node1)
+
+"""
+    Given a 'start' node and a 'graph', call visitFunc
+    sequentially on the current node, and then its children
+    and so forth.
+    When visiting each node, mark it as visited by adding it to the hashmap.
+    Then queue up all of its children to be visited next.
+"""
+def bfs(start, graph, visitFunc=visitPrint):
+    visited = collections.defaultdict(bool)
+    queue = collections.deque()
+
+    queue.append(start)
+
+    while(len(queue) > 0):
+        current = queue.popleft()
+
+        if (not visited[current]):
+            visited[current] = True
+            visitFunc(current)
+            for neighbor in graph.adjList[current]:
+                queue.append(neighbor)
+
+# Testing the breadth first search implementation
+if __name__ == "__main__":
+
+    # Testing on this tree
+    #      1
+    #     / \
+    #    /   \
+    #   2     3
+    #  / \   / \
+    # 4   5 6   7
+
+    g = Graph()
+    g.addEdge(1, 2)
+    g.addEdge(1, 3)
+    g.addEdge(2, 4)
+    g.addEdge(2, 5)
+    g.addEdge(3, 6)
+    g.addEdge(3, 7)
+
+    print("Test 1:")
+    bfs(1, g)
+
+    print("\nTest2:")
+    bfs(2, g)

Graph_Algorithms/src/Depth_First_Traversal/DFS.py

@@ -0,0 +1,54 @@
+#DFS by Master-Fury
+import collections
+
+class Graph:
+    def __init__(self):
+        self.adjList = collections.defaultdict(set)
+
+    def addEdge(self, node1, node2):
+        self.adjList[node1].add(node2)
+        self.adjList[node2].add(node1)
+
+def dfsHelper(current, graph, visited, visitFunc):
+    if (visited[current]):
+        return
+    
+    visited[current] = True;
+    
+    visitFunc(current)
+    
+    for neighbor in graph.adjList[current]:
+        dfsHelper(neighbor, graph, visited, visitFunc)
+    
+
+def dfs(current, graph, visitFunc):
+    visited = collections.defaultdict(bool)
+    dfsHelper(current, graph, visited, visitFunc)
+
+def visitPrint(i):
+    print(i)
+
+# Testing the depth first search implementation
+if __name__ == "__main__":
+
+    # Testing on this tree
+    #      1
+    #     / \
+    #    /   \
+    #   2     3
+    #  / \   / \
+    # 4   5 6   7
+    
+    g = Graph()
+    g.addEdge(1, 2)
+    g.addEdge(1, 3)
+    g.addEdge(2, 4)
+    g.addEdge(2, 5)
+    g.addEdge(3, 6)
+    g.addEdge(3, 7)
+
+    print("Test 1:")
+    dfs(1, g, visitPrint)
+    
+    print("\nTest2:")
+    dfs(2, g, visitPrint)