如何在Java中实现DFS和BFS函数？

深度优先搜索（DFS）和广度优先搜索（BFS）是常用的图遍历算法。在Java中，我们可以使用递归或者栈来实现DFS，使用队列来实现BFS。

DFS的实现：

递归法：

class Graph {
    private int V; // 顶点数量
    private LinkedList<Integer> adj[]; // 邻接表

    Graph(int v) {
        V = v;
        adj = new LinkedList[v];
        for (int i = 0; i < v; ++i) {
            adj[i] = new LinkedList<>();
        }
    }

    void addEdge(int v, int w) {
        adj[v].add(w);
    }

    void DFSUtil(int v, boolean visited[]) {
        visited[v] = true;
        System.out.print(v + " ");

        Iterator<Integer> i = adj[v].listIterator();
        while (i.hasNext()) {
            int n = i.next();
            if (!visited[n])
                DFSUtil(n, visited);
        }
    }

    void DFS(int v) {
        boolean visited[] = new boolean[V];
        DFSUtil(v, visited);
    }
}

public class Main {
    public static void main(String args[]) {
        Graph g = new Graph(4);

        g.addEdge(0, 1);
        g.addEdge(0, 2);
        g.addEdge(1, 2);
        g.addEdge(2, 0);
        g.addEdge(2, 3);
        g.addEdge(3, 3);

        System.out.println("Following is Depth First Traversal (starting from vertex 2):");

        g.DFS(2);
    }
}

栈法：

import java.util.*;

class Graph {
    private int V; // 顶点数量
    private LinkedList<Integer> adj[]; // 邻接表

    Graph(int v) {
        V = v;
        adj = new LinkedList[v];
        for (int i = 0; i < v; ++i) {
            adj[i] = new LinkedList<>();
        }
    }

    void addEdge(int v, int w) {
        adj[v].add(w);
    }

    void DFS(int v) {
        boolean visited[] = new boolean[V];

        Stack<Integer> stack = new Stack<>();

        visited[v] = true;
        stack.push(v);

        while (stack.size() != 0) {
            v = stack.pop();
            System.out.print(v + " ");

            Iterator<Integer> i = adj[v].listIterator();
            while (i.hasNext()) {
                int n = i.next();
                if (!visited[n]) {
                    visited[n] = true;
                    stack.push(n);
                }
            }
        }
    }
}

public class Main {
    public static void main(String args[]) {
        Graph g = new Graph(4);

        g.addEdge(0, 1);
        g.addEdge(0, 2);
        g.addEdge(1, 2);
        g.addEdge(2, 0);
        g.addEdge(2, 3);
        g.addEdge(3, 3);

        System.out.println("Following is Depth First Traversal (starting from vertex 2):");

        g.DFS(2);
    }
}

BFS的实现：

import java.util.*;

class Graph {
    private int V; // 顶点数量
    private LinkedList<Integer> adj[]; // 邻接表

    Graph(int v) {
        V = v;
        adj = new LinkedList[v];
        for (int i = 0; i < v; ++i) {
            adj[i] = new LinkedList<>();
        }
    }

    void addEdge(int v, int w) {
        adj[v].add(w);
    }

    void BFS(int v) {
        boolean visited[] = new boolean[V];

        LinkedList<Integer> queue = new LinkedList<>();

        visited[v] = true;
        queue.add(v);

        while (queue.size() != 0) {
            v = queue.poll();
            System.out.print(v + " ");

            Iterator<Integer> i = adj[v].listIterator();
            while (i.hasNext()) {
                int n = i.next();
                if (!visited[n]) {
                    visited[n] = true;
                    queue.add(n);
                }
            }
        }
    }
}

public class Main {
    public static void main(String args[]) {
        Graph g = new Graph(4);

        g.addEdge(0, 1);
        g.addEdge(0, 2);
        g.addEdge(1, 2);
        g.addEdge(2, 0);
        g.addEdge(2, 3);
        g.addEdge(3, 3);

        System.out.println("Following is Breadth First Traversal (starting from vertex 2):");

        g.BFS(2);
    }
}

以上就是在Java中实现DFS和BFS函数的方法，可以根据需要选择递归或者栈来实现DFS，使用队列来实现BFS。