I need some help with the DFS function below, while the algorithm for it is an iterative one, I can not figure out how to implement it in my code.
package graphexample;
import java.util.*;
class GraphExample {
class Edge {
int v, w;
public Edge(int v, int w){
this.v = v;
this.w =w;
}
@Override
public String toString(){
return "("+v+","+w+")";
}
}
List<Edge> G[];
boolean marked [];
public GraphExample(int n){
G = new LinkedList[n];
marked = new boolean [n];
Arrays.fill(marked, false);
for (int i = 0; i < G.length; i++) {
G[i]=new LinkedList<Edge>();
}
}
@Override
public String toString(){
String result = "";
for (int i = 0; i < G.length; i++)
result+=i+"=>"+G[i]+"\n";
return result;
}
boolean isConnected (int u, int v){
for (Edge i:G[u])
if(i.w==v) return true;
return false;
}
/* @param args the command line arguments
*/
void addEdge(int u, int v, int w){
G[u].add(0,new Edge(v,w));
}
Below is the function, which I am stuck on. I know I need to set it up in a way, which I can call dfs() again. As it is, it finds some of the connected edges when I increment v also, but it misses edge 3,1 and 4,0 which are edges with initial node having a higher index than the one it is mapped to. void dfs(int v){
for (int i = 0; i < G.length; i++) {
if(isConnected(i,v))
marked[i]=true;
//System.out.println("i:"+i+"v:"+v);
}
for (int i = 0; i < G.length; i++) {
if(marked[i]==true)
System.out.println("Here is a connected node"+G[i]);
}
}
public static void main(String[] args) {
GraphExample g = new GraphExample(5);
g.addEdge(0,0,1);
g.addEdge(1, 1, 3);
g.addEdge(3, 3, 1);
g.addEdge(1, 1, 2);
g.addEdge(2, 2, 4);
g.addEdge(4, 4, 0);
System.out.println(g);
System.out.println("Is node 2 connected to node 4?"+g.isConnected(4, 0));
g.dfs(0);
}
}
Thank you for your help. Below I have posted the updated code with Depth and Breadth First Modules. I would appreciate some feedback on whether the BFS section is correct, and if there is a better way of accomplishing the task. Note: this is not an assignment of any sort.
package graphexample;
import java.util.*;
class GraphExample {
class Edge {
int v, w;
public Edge(int v, int w){
this.v = v;
this.w =w;
}
@Override
public String toString(){
return "("+v+","+w+")";
}
}
List<Edge> G[];
//boolean marked [];
public GraphExample(int n){
G = new LinkedList[n];
//marked = new boolean [n];
//Arrays.fill(marked, false);
for (int i = 0; i < G.length; i++) {
G[i]=new LinkedList<Edge>();
}
}
@Override
public String toString(){
String result = "";
for (int i = 0; i < G.length; i++)
result+=i+"=>"+G[i]+"\n";
return result;
}
boolean isConnected (int u, int v){
for (Edge i:G[u])
if(i.w==v) return true;
return false;
}
int getVertex (GraphExample G[], int v){
int i;
return 0;
}
/* @param args the command line arguments
*/
void addEdge(int u, int v, int w){
G[u].add(0,new Edge(v,w));
}
void DFSUtil(int v, boolean [] visited) {
visited[v] = true;
System.out.println("DFS: Just visited"+v+" ");
Iterator<Edge> i = G[v].listIterator();
while (i.hasNext())
{
int n = i.next().w;
if (!visited[n])
DFSUtil(n, visited);
}
}
void dfs(int v){
boolean visited[];
visited = new boolean[G.length];
// Call the recursive helper function to print DFS traversal
DFSUtil(v, visited);
}
void bfs(int v){
boolean visited[];
visited = new boolean[G.length];
visited[v]=true;
Queue q = new LinkedList();
for (int i = 0; i < G.length; i++) {
q.add(i);
}
//System.out.println("Here is what is in the Queue"+q);
while (!q.isEmpty()) {
int s = (int)q.poll();//I am not sure if casting is a ok or if there
//is a better way
//System.out.println("This is from Queue during BFS:"+s);
Iterator<Edge> It = G[s].listIterator();
while(It.hasNext()){
Edge n = It.next();
if (!visited[n.w]){
visited[n.w]=true;
q.add(n.w);
System.out.println("BFS: Just visited"+n.w);}
}
}
}
public static void main(String[] args) {
GraphExample g = new GraphExample(5);
g.addEdge(0,0,1);
g.addEdge(1, 1, 3);
g.addEdge(3, 3, 1);
g.addEdge(1, 1, 2);
g.addEdge(2, 2, 4);
g.addEdge(4, 4, 0);
System.out.println(g);
System.out.println("Is node 2 connected to node 4?"+g.isConnected(4, 0));
g.dfs(0);
g.bfs(0);
}
}
void DFSUtil(int v,boolean visited[])
{
visited[v] = true;
System.out.print(v+" ");
Iterator<Integer> i = adj[v].listIterator();
while (i.hasNext())
{
int n = i.next();
if (!visited[n])
DFSUtil(n, visited);
}
}
void DFS(int v)
{
boolean visited[] = new boolean[V];
// Call the recursive helper function to print DFS traversal
DFSUtil(v, visited);
}