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April 20, 2016 14:59
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| package graphs; | |
| import java.util.Arrays; | |
| import java.util.Stack; | |
| public class DFS { | |
| private Color[] colors; | |
| private Integer[] predecessors; | |
| private Integer[] distances; | |
| private Graph graph; | |
| boolean debug = true; | |
| public enum Color { | |
| WHITE, GRAY, BLACK; | |
| } | |
| public DFS(Graph g_) { | |
| graph = g_; | |
| colors = new Color[g_.V()]; | |
| predecessors = new Integer[g_.V()]; | |
| distances = new Integer[g_.V()]; | |
| } | |
| public void dfs(int source) { | |
| if (source < 0 || source >= graph.V()) { | |
| throw new IndexOutOfBoundsException(); | |
| } | |
| for (int u = 0; u < graph.V(); u++) { | |
| if (u != source) { | |
| colors[u] = Color.WHITE; | |
| distances[u] = Integer.MAX_VALUE; | |
| predecessors[u] = null; | |
| } | |
| } | |
| colors[source] = Color.GRAY; | |
| distances[source] = 0; | |
| predecessors[source] = null; | |
| Stack<Integer> q = new Stack<Integer>(); | |
| q.add(source); | |
| while (!q.isEmpty()) { | |
| Integer u = q.pop(); | |
| for (Integer v : graph.adj(u)) { | |
| if (colors[v] == Color.WHITE) { | |
| colors[v] = Color.GRAY; | |
| distances[v] = distances[u] + 1; | |
| predecessors[v] = u; | |
| q.add(v); | |
| } | |
| } | |
| colors[u] = Color.BLACK; | |
| if (debug) { | |
| System.out.println(this); | |
| } | |
| } | |
| } | |
| public String toString() { | |
| StringBuilder sb = new StringBuilder(); | |
| sb.append(Arrays.toString(colors)); | |
| sb.append("\n"); | |
| sb.append(Arrays.toString(distances)); | |
| sb.append("\n"); | |
| sb.append(Arrays.toString(predecessors)); | |
| sb.append("\n"); | |
| return new String(sb); | |
| } | |
| public static void main(String[] args) { | |
| int V = 8; | |
| Graph g = new Graph(V); | |
| g.addUndirectedEdge(0, 1); | |
| g.addUndirectedEdge(1, 2); | |
| g.addUndirectedEdge(2, 3); | |
| g.addUndirectedEdge(3, 4); | |
| g.addUndirectedEdge(3, 5); | |
| g.addUndirectedEdge(4, 5); | |
| g.addUndirectedEdge(5, 6); | |
| g.addUndirectedEdge(4, 7); | |
| g.addUndirectedEdge(6, 7); | |
| System.out.println(g); | |
| DFS dfs = new DFS(g); | |
| dfs.dfs(0); | |
| System.out.println(dfs); | |
| } | |
| } |
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