4.2---找图的两个节点是否有路径

//这道题AC了，但是并不确定是否完全正确。此外要注意因为是有向图，所以既要检查a到b，还要检查b到a
public class Path {
  
    public boolean checkPath(UndirectedGraphNode a, UndirectedGraphNode b) {
        return checkPath2(a,b) || checkPath2(b,a);
    }
    public boolean checkPath2(UndirectedGraphNode a, UndirectedGraphNode b) {

        boolean res = false;
        if(a.label == b.label) return true;
        if(a.neighbors == null) return false;
        for(UndirectedGraphNode temp : a.neighbors){
            if(temp.label == -1){
                return false;
            }
            else{
                temp.label = -1;
            }
            if(checkPath(temp,b)){
                return true;
            }
        }
        return res;
    }
}