图的深度优先遍历寻路算法

图的深度优先遍历寻路算法

看注释吧

package GraphBasics;

import java.util.Stack;
import java.util.Vector;

/**
 * @ Description:深度优先遍历寻路算法
 * @ Date: Created in 12:53 2018/8/1
 * @ Author: Anthony_Duan
 */
public class Path {
    private Graph G;
    private int s;
    private boolean[] visited;
    private int[] from;


    //图的深度优先遍历
    private void dfs(int v) {
        visited[v] = true;
        for (int i :
                G.adj(v)) {
            if (!visited[i]) {
                from[i] = v;
                dfs(i);
            }
        }
    }

    //构造函数，寻路算法，寻找图Graph从s点到其他点的路径
    public Path(Graph graph, int s) {
        //算法初始化
        G = graph;
        assert s >= 0 && s < G.V();

        visited = new boolean[G.V()];
        from = new int[G.V()];
        for (int i = 0; i < G.V(); i++) {
            visited[i] = false;
            from[i] = -1;
        }
        this.s = s;
        //寻路算法
        dfs(s);
    }

    //查询从s点到w点是否有路径
    boolean hasPath(int w) {
        assert w >= 0 && w < G.V();
        return visited[w];
    }

    //查询从s点到w点的路径存放在vec中
    Vector path(int w) {
        assert hasPath(w);

        Stack s = new Stack<>();
        //通过from数组逆向查找到从s到w的路径，存到栈中
        int p = w;
        while (p != -1) {
            s.push(p);
            p = from[p];
        }

        //从栈中依次取出元素，获得顺序的从s到w的路径
        Vector res = new Vector<>();
        while (!s.empty()) {
            res.add(s.pop());
        }
        return res;
    }

    //打印出从s点到w点的路径
    void showPath(int w) {
        assert hasPath(w);
        Vector vec = path(w);
        for (int i = 0; i < vec.size(); i++) {
            System.out.println(vec.elementAt(i));
            if (i == vec.size() - 1) {
                System.out.println();
            } else {
                System.out.print("->");
            }
        }
    }
}