java如何实现拓扑图-乐工具技术知识

在Java中，实现拓扑图可以通过使用邻接表或邻接矩阵来表示图。这里我将给出一个使用邻接表实现的简单示例。拓扑图是有向无环图（Directed Acyclic Graph，简称DAG）的一种应用场景。

首先，我们需要创建一个表示图的类，包括顶点和边。然后，我们可以使用深度优先搜索（DFS）或广度优先搜索（BFS）来遍历图并实现拓扑排序。

以下是一个简单的实现：

定义顶点类（Vertex）：

public class Vertex {
    private String label;
    private List neighbors;

    public Vertex(String label) {
        this.label = label;
        this.neighbors = new ArrayList<>();
    }

    public void addNeighbor(Vertex neighbor) {
        this.neighbors.add(neighbor);
    }

    public String getLabel() {
        return label;
    }

    public List getNeighbors() {
        return neighbors;
    }
}

定义图类（Graph）：

public class Graph {
    private List vertices;

    public Graph() {
        this.vertices = new ArrayList<>();
    }

    public void addVertex(Vertex vertex) {
        this.vertices.add(vertex);
    }

    public List getVertices() {
        return vertices;
    }
}

实现拓扑排序（Topological Sort）：

public class TopologicalSort {
    public static List topologicalSort(Graph graph) {
        List sortedVertices = new ArrayList<>();
        Set visitedVertices = new HashSet<>();

        for (Vertex vertex : graph.getVertices()) {
            if (!visitedVertices.contains(vertex)) {
                dfs(vertex, visitedVertices, sortedVertices);
            }
        }

        Collections.reverse(sortedVertices);
        return sortedVertices;
    }

    private static void dfs(Vertex currentVertex, Set visitedVertices, List sortedVertices) {
        visitedVertices.add(currentVertex);

        for (Vertex neighbor : currentVertex.getNeighbors()) {
            if (!visitedVertices.contains(neighbor)) {
                dfs(neighbor, visitedVertices, sortedVertices);
            }
        }

        sortedVertices.add(currentVertex);
    }
}

测试拓扑排序：

public class Main {
    public static void main(String[] args) {
        Graph graph = new Graph();

        Vertex v1 = new Vertex("1");
        Vertex v2 = new Vertex("2");
        Vertex v3 = new Vertex("3");
        Vertex v4 = new Vertex("4");
        Vertex v5 = new Vertex("5");

        graph.addVertex(v1);
        graph.addVertex(v2);
        graph.addVertex(v3);
        graph.addVertex(v4);
        graph.addVertex(v5);

        v1.addNeighbor(v2);
        v1.addNeighbor(v3);
        v2.addNeighbor(v4);
        v3.addNeighbor(v4);
        v4.addNeighbor(v5);

        List sortedVertices = TopologicalSort.topologicalSort(graph);

        for (Vertex vertex : sortedVertices) {
            System.out.print(vertex.getLabel() + " ");
        }
    }
}

输出结果：