From f80dce4991c29c9ab963c474ec7638eb096cb0eb Mon Sep 17 00:00:00 2001
From: Luigi Santocanale <luigi.santocanale@lif.univ-mrs.fr>
Date: Fri, 6 Dec 2019 08:38:36 +0100
Subject: [PATCH] Added BreadthFirstSearch.java
---
src/BreadthFirstSearch.java | 46 +++++++++++++++++++++++++++++++++++++
1 file changed, 46 insertions(+)
create mode 100644 src/BreadthFirstSearch.java
diff --git a/src/BreadthFirstSearch.java b/src/BreadthFirstSearch.java
new file mode 100644
index 0000000..f370f25
--- /dev/null
+++ b/src/BreadthFirstSearch.java
@@ -0,0 +1,46 @@
+import java.util.ArrayList;
+import java.util.BitSet;
+import java.util.LinkedList;
+import java.util.Queue;
+
+
+public class BreadthFirstSearch {
+
+ Graph graph;
+ Queue<Arc> frontier;
+ ArrayList<Arc> tree;
+ BitSet reached;
+
+ private void push(int vertex) {
+ for (Arc arc : graph.outNeighbours(vertex)) frontier.offer(arc);
+ }
+
+ private void explore(Arc nextArc) {
+ if (reached.get(nextArc.getDest())) return;
+ reached.set(nextArc.getDest());
+ tree.add(nextArc);
+ push(nextArc.getDest());
+ }
+
+ private void bfs(int startingVertex) {
+ reached.set(startingVertex);
+ push(startingVertex);
+ while (!frontier.isEmpty()) {
+ explore(frontier.poll());
+ }
+ }
+
+ private BreadthFirstSearch (Graph graph) {
+ this.graph = graph;
+ this.frontier = new LinkedList<>();
+ this.tree = new ArrayList<>();
+ this.reached = new BitSet(graph.order);
+ }
+
+ public static ArrayList<Arc> generateTree(Graph graph, int root) {
+ BreadthFirstSearch algo = new BreadthFirstSearch(graph);
+ algo.bfs(root);
+ return algo.tree;
+ }
+
+}
--
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