[广度遍历和深度遍历]聊聊算法和设计模式

Posted 2020-07-28 风雨彩虹

晚上无聊写了个二叉树（图）的广度和深度遍历算法，算法本身很简单，但是如何做到通用呢，一下代码是我的设计，请大家帮忙看看有什么问题，我自己感觉有问题就是不知道具体什么问题

    public interface IGraph<TVertex>
    {
        IEnumerable<IEdge<TVertex>> Edges { get; }
    }

    public interface IEdge<TVertex>
    {
        TVertex From { get; set; }
        TVertex To { get; set; }
    }

    public interface INode
    {
        IEnumerable<TNode> GetNextNodes<TNode>() where TNode : INode;
    }

    public class Edge<TVertex> : IEdge<TVertex>
    {
        public TVertex From { get; set; }
        public TVertex To { get; set; }
    }

    public static class NodeVisitor
    {
        public static void BreadthVisit<TNode>(TNode rootNode, Action<TNode> visitAction)
           where TNode : INode
        {
            BreadthVisit(rootNode, n => n.GetNextNodes<TNode>(), visitAction);
        }

        public static void BreadthVisit<TNode>(TNode rootNode, Func<TNode,IEnumerable<TNode>> nextNodeSelector, Action<TNode> visitAction)
        {
            var nodeQueue = new Queue<TNode>();
            nodeQueue.Enqueue(rootNode);
            while (nodeQueue.Any())
            {
                var currentNode = nodeQueue.Dequeue();
                if (visitAction != null)
                {
                    visitAction(currentNode);
                }
                foreach (var nextNode in nextNodeSelector(currentNode))
                {
                    nodeQueue.Enqueue(nextNode);
                }
            }
        }

        public static void DepthVisit<TNode>(TNode rootNode, Func<TNode, IEnumerable<TNode>> nextNodeSelector, Action<TNode> visitAction)
        {
            var nodeStack = new Stack<TNode>();
            nodeStack.Push(rootNode);
            while (nodeStack.Any())
            {
                var currentNode = nodeStack.Pop();
                if (visitAction != null)
                {
                    visitAction(currentNode);
                }
                foreach (var nextNode in nextNodeSeletor(currentNode))
                {
                    nodeStack.Push(nextNode);
                }
            }
        }

        public static void DepthVisit<TNode>(TNode rootNode, Action<TNode> visitAction)
           where TNode : INode
        {
            DepthVisit(rootNode, n => n.GetNextNodes<TNode>(), visitAction);
        }
    }

    public class GraphVisitor<TVertex> 
    {
        private IGraph<TVertex> _graph;

        public GraphVisitor(IGraph<TVertex> graph)
        {
            _graph = graph;
        }

        public TVertex GetRoot()
        {
            var vertexs = _graph.Edges.Select(t => t.From).Concat(_graph.Edges.Select(t => t.To));
            var toVertexs = _graph.Edges.Select(t => t.To);
            return vertexs.FirstOrDefault(t => toVertexs.All(v => !v.Equals(t)));
        }

        public IEnumerable<TVertex> GetNextVertexs(TVertex current)
        {
            return _graph.Edges.Where(t => t.From.Equals(current)).Select(t => t.To);
        }

        public void BreadthVisit(Action<TVertex> visitAction, TVertex startVertex)
        {
            NodeVisitor.BreadthVisit(startVertex, t => GetNextVertexs(t), visitAction);
        }

        public void BreadthVisit(Action<TVertex> visitAction)
        {
            NodeVisitor.BreadthVisit(GetRoot(), t => GetNextVertexs(t), visitAction);
        }

        public void DepthVisit(Action<TVertex> visitAction, TVertex startVertex)
        {
            NodeVisitor.DepthVisit(startVertex, t => GetNextVertexs(t), visitAction);
        }

        public void DepthVisit(Action<TVertex> visitAction)
        {
            NodeVisitor.DepthVisit(GetRoot(), t => GetNextVertexs(t), visitAction);
        }

        private class GraphNode : INode
        {
            private IList<INode> nodes = new List<INode>();

            public string Id { get; set; }

            public void AddNext(INode node)
            {
                nodes.Add(node);
            }

            public IEnumerable<TNode> GetNextNodes<TNode>() where TNode : INode
            {
                return nodes.Cast<TNode>();
            }
        }
    }

 单元测试代码：

    [TestClass]
    public class BreadthVisitorTest
    {
        [TestMethod]
        public void TestVisit()
        {
            var node1 = new TestNode() { Id = "1" };

            var node1_1 = new TestNode() { Id = "1_1" };
            var node1_2 = new TestNode() { Id = "1_2" };

            var node1_1_1 = new TestNode() { Id = "1_1_1" };
            var node1_1_2 = new TestNode() { Id = "1_1_2" };
            var node1_1_3 = new TestNode() { Id = "1_1_3" };

            var node1_2_1 = new TestNode() { Id = "1_2_1" };
            var node1_2_2 = new TestNode() { Id = "1_2_2" };

            node1.AddNext(node1_1);
            node1.AddNext(node1_2);

            node1_1.AddNext(node1_1_1);
            node1_1.AddNext(node1_1_2);
            node1_1.AddNext(node1_1_3);

            node1_2.AddNext(node1_2_1);
            node1_2.AddNext(node1_2_2);
            var expected = "1.1_1.1_2.1_1_1.1_1_2.1_1_3.1_2_1.1_2_2";
            var actual = "";
            NodeVisitor.BreadthVisit(node1, n => {
                actual += n.Id + ".";
            });

            Assert.AreEqual(expected, actual.Trim(\'.\'));

            expected = "1.1_1.1_1_1.1_1_2.1_1_3.1_2.1_2_1.1_2_2";
            actual = "";
            NodeVisitor.DepthVisit(node1, n => {
                actual += n.Id + ".";
            });
        }

        [TestMethod]
        public void TestGraphVisit()
        {
            var graph = new Graph();
            var graphVisitor = new GraphVisitor<int>(graph);

            graph.AddEdge(1, 2);
            graph.AddEdge(1, 3);

            graph.AddEdge(2, 4);
            graph.AddEdge(2, 5);

            graph.AddEdge(3, 6);

            var expected = "123456";
            var actual = "";

            graphVisitor.BreadthVisit(a => { actual += a.ToString(); });

            Assert.AreEqual(expected, actual);

            expected = "124536";
            actual = "";
            graphVisitor.DepthVisit(a => { actual += a.ToString(); });

        }
    }

    public class TestNode : INode
    {
        private IList<INode> nodes = new List<INode>();

        public string Id { get; set; }

        public void AddNext(INode node)
        {
            nodes.Add(node);
        }

        public IEnumerable<TNode> GetNextNodes<TNode>() where TNode : INode
        {
            return nodes.Cast<TNode>();
        }
    }

    public class Graph : IGraph<int>
    {
        private IList<IEdge<int>> _edges = new List<IEdge<int>>();
        public IEnumerable<IEdge<int>> Edges
        {
            get
            {
                return _edges;
            }
        }

        public void AddEdge(int from, int to)
        {
            _edges.Add(new Edge<int>() { From = from, To = to });
        }
    }

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