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DepthFirstSearch.java
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61 lines (54 loc) · 1.43 KB
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/**
* Run depth first search
*
*/
public class DepthFirstSearch {
private boolean[] marked; // marked[v] = is there an s-v path?
private int count; // number of vertices connected to s
// Computes the vertices in graph `G` that are connected to the source vertex `s`
public DepthFirstSearch(Graph G, int s) {
marked = new boolean[G.V()];
validateVertex(s);
dfs(G, s);
}
// depth first search from v
private void dfs(Graph G, int v) {
count++;
marked[v] = true;
for(int w:G.adj(v)) {
if(!marked[w])
dfs(G, w);
}
}
// Is there a path between the source vertex `s` and vertex `v`?
public boolean marked(int v) {
validateVertex(v);
return marked[v];
}
// Returns the number of vertices connected to the source vertex `s`
public int count() {
return count;
}
// throw an IllegalArgumentException unless `0 <= v < V`
private void validateVertex(int v) {
int V = marked.length;
if(v < 0 || v >= V)
throw new IllegalArgumentException("vertex " + V + "is not between 0 and " + (V - 1));
}
// test
public static void main(String[] args) {
In in = new In(args[0]);
Graph G = new Graph(in);
int s = Integer.parseInt(args[1]);
DepthFirstSearch search = new DepthFirstSearch(G, s);
for(int v = 0; v < G.V(); v++) {
if(search.marked(v))
StdOut.print(v + " ");
}
StdOut.println();
if(search.count() != G.V())
StdOut.println("NOT connected");
else
StdOut.println("connected");
}
}