Route Between Two Nodes in Graph
LintCode-176.Route Between Two Nodes in Graph
Given a directed graph, design an algorithm to find out whether there is a route between two nodes.
Example
Given graph:
A----->B----->C
\ |
\ |
\ |
\ v
->D----->E
for s = B and t = E, return true
for s = D and t = C, return false
/**
* Definition for Directed graph.
* class DirectedGraphNode {
* int label;
* ArrayList<DirectedGraphNode> neighbors;
* DirectedGraphNode(int x) {
* label = x;
* neighbors = new ArrayList<DirectedGraphNode>();
* }
* };
*/
public class Solution {
/**
* @param graph: A list of Directed graph node
* @param s: the starting Directed graph node
* @param t: the terminal Directed graph node
* @return: a boolean value
*/
public boolean hasRoute(ArrayList<DirectedGraphNode> graph,
DirectedGraphNode s, DirectedGraphNode t) {
if (graph == null || graph.size() == 0) {
return true;
}
Set<DirectedGraphNode> visited = new HashSet<>();
return dfs(s, t, visited);
}
boolean dfs(DirectedGraphNode s, DirectedGraphNode t, Set<DirectedGraphNode> visited) {
if (s == t) {
return true;
}
visited.add(s);
for (DirectedGraphNode n : s.neighbors) {
if (!visited.contains(n)) {
if (dfs(n, t, visited)) {
return true;
}
}
}
return false;
}
}
Hope this helps,
Michael