added python dfs and bfs

Author: Morfly

src/python/Stub.py renamed to src/python/BUILD

@@ -0,0 +1 @@
+workspace(name = "algorithms_python")

src/python/WORKSPACE

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+py_binary(
+    name = "bfs",
+    main = "breadth_first_traversal.py",
+    srcs = glob(["*.py"]),
+)

src/python/sequential/graph/bfs/BUILD

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+import collections
+
+
+def bfs(graph, root):
+    """
+    Performs breadth-first traversal on the :param graph: starting from the :param root: node.
+    """
+    explored = set()
+    traversed = []
+    search_queue = collections.deque()
+
+    search_queue.append(root)
+    while search_queue:
+        node = search_queue.popleft()
+        if node not in explored:
+            explored.add(node)
+            traversed.append(node)
+            search_queue += graph.get(node, [])
+
+    return traversed
+
+
+def main():
+    graph = {
+        "you": ["alice", "bob", "clair"],
+        "alice": ["peggy"],
+        "clair": ["thom", "jonny"],
+        "bob": ["anuj", "peggy"],
+    }
+
+    print(
+        bfs(graph, "you")
+    )
+
+
+if __name__ == "__main__":
+    main()

src/python/sequential/graph/bfs/breadth_first_traversal.py

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+py_binary(
+    name = "dfs_iterative",
+    main = "iterative_depth_first_traversal.py",
+    srcs = ["iterative_depth_first_traversal.py"],
+)
+
+py_binary(
+    name = "dfs_recursive",
+    main = "recursive_depth_first_traversal.py",
+    srcs = ["recursive_depth_first_traversal.py"],
+)

src/python/sequential/graph/dfs/BUILD

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+import collections
+
+
+def dfs(graph, root):
+    """
+    Performs iterative depth-first traversal on the :param graph: starting from the :param root: node.
+    """
+    explored = set()
+    traversed = []
+    search_stack = collections.deque()
+
+    search_stack.append(root)
+    while search_stack:
+        node = search_stack.pop()
+        if node not in explored:
+            explored.add(node)
+            traversed.append(node)
+            search_stack += graph.get(node, [])
+
+    return traversed
+
+
+def main():
+    graph = {
+        "you": ["alice", "bob", "clair"],
+        "alice": ["peggy"],
+        "clair": ["thom", "jonny"],
+        "bob": ["anuj", "peggy"],
+    }
+
+    print(
+        dfs(graph, "you")
+    )
+
+
+if __name__ == "__main__":
+    main()

src/python/sequential/graph/dfs/iterative_depth_first_traversal.py

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+def dfs(graph, root):
+    """
+    Performs recursive depth-first traversal on the :param graph: starting from the :param root: node.
+    """
+    explored = set()
+    traversed = []
+
+    def explore(node):
+        explored.add(node)
+        traversed.append(node)
+
+        successors = graph.get(node, [])
+        for succ in successors:
+            if succ not in explored:
+                explore(succ)
+
+    explore(root)
+
+    return traversed
+
+
+def main():
+    graph = {
+        "you": ["alice", "bob", "clair"],
+        "alice": ["peggy"],
+        "clair": ["thom", "jonny"],
+        "bob": ["anuj", "peggy"],
+    }
+
+    print(
+        dfs(graph, "you")
+    )
+
+if __name__ == "__main__":
+    main()