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;
}
}