*13. Forward path checking

Title Description

For a forward graph, implement an algorithm to find out if there is a path between two points.

The pointer to the two nodes in the given figure undirectedgraphnode* a, undirectedgraphnode*b(please do not care about the data type, the graph is a graph), please return a bool, Represents whether there is a path between two points (A to B or B to a).

Thought: Breadth First search

The template code is as follows:

Public  enum state{    unvisited,visited,visiting;} public static Boolean search (Grapth g,node Start,node end) {    //as queue using    linkedlist<node> q=new LinkedList <Node> ();    For (Node u:g.getnodes ()) {       u.state=state.unvisited;    }    start.state=state.visiting;    Q.add (start);    Node u; while    (!q.isempty ()) {        u=q.removefirst ();        if (u!=null) {for           (Node v:u.getadjacent ()) {             if (v.state==state.unvisited) {                 if (v==end) {                     return true;                 } else{                     v.state=state.visiting;                     Q.add (v);         }} u.state=state.visited;        }    }    return false;}

　　

Method 2: Doubt. The code is as follows:

Import Java.util.*;/*public class Undirectedgraphnode {    int label = 0;    Undirectedgraphnode left = null;    Undirectedgraphnode right = null;    arraylist<undirectedgraphnode> neighbors = new arraylist<undirectedgraphnode> ();    public undirectedgraphnode (int label) {        this.label = label;    }} */public class Path {public    boolean checkpath (Undirectedgraphnode A, Undirectedgraphnode b) {               return check (b) || Check (b,a);    }    Boolean check (Undirectedgraphnode A, Undirectedgraphnode b) {        if (a==b) return true;        for (int i=0;i<a.neighbors.size (); i++) {            return check (A.neighbors.get (i), b);        }        return false;    }}

　　

*13. Forward path checking