NonrecursiveDFS

賈小強
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package com.lab1.test6;

import java.util.Iterator;

import com.lab1.test1.LinkedStack;

public class NonrecursiveDFS {
    private boolean[] marked; // marked[v] = is there an s-v path?
    private int[] edgeTo;
    private int s;

    public NonrecursiveDFS(Graph graph, int s) {
        marked = new boolean[graph.V()];
        edgeTo = new int[graph.V()];
        this.s = s;
        validateVertex(s);

        dfs(graph, s);
    }

    private void dfs(Graph graph, int s) {
        Iterator[] adj = (Iterator[]) new Iterator[graph.V()];
        for (int v = 0; v < graph.V(); v++)
            adj[v] = graph.adj(v).iterator();

        LinkedStack stack = new LinkedStack();
        marked[s] = true;
        stack.push(s);
        while (!stack.isEmpty()) {
            int v = stack.peek();
            if (adj[v].hasNext()) {
                int w = adj[v].next();
                if (!marked[w]) {
                    marked[w] = true;
                    edgeTo[w] = v;
                    stack.push(w);
                }
            } else {
                stack.pop();
            }
        }
    }

    private Iterable pathTo(int v) {
        LinkedStack stack = new LinkedStack<>();
        for (int x = v; x != s; x = edgeTo[x]) {
            stack.push(x);
        }
        stack.push(s);
        return stack;
    }

    private boolean hashPathTo(int v) {
        return marked[v];
    }

    private void validateVertex(int v) {
        int V = marked.length;
        if (v < 0 || v >= V)
            throw new IllegalArgumentException("vertex " + v + " is not between 0 and " + (V - 1));
    }

    public static void main(String[] args) {
        int[][] edges = { { 0, 5 }, { 2, 4 }, { 2, 3 }, { 1, 2 }, { 0, 1 }, { 3, 4 }, { 3, 5 }, { 0, 2 } };
        Graph graph = new Graph(edges);
        int s = 0;
        NonrecursiveDFS dfs = new NonrecursiveDFS(graph, s);
        for (int v = 0; v < graph.V(); v++) {
            if (dfs.hashPathTo(v)) {
                System.out.print(s + " to " + v + " : ");
                for (int x : dfs.pathTo(v)) {
                    System.out.print(x + " ");
                }
                System.out.println();
            } else {
                System.out.println(s + " to " + v + "Not Connected");
            }
        }
    }

}

输出

0 to 0 : 0 
0 to 1 : 0 2 1 
0 to 2 : 0 2 
0 to 3 : 0 2 3 
0 to 4 : 0 2 3 4 
0 to 5 : 0 2 3 5 

Happy learning !!