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Commit 12665dc

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added bfs to graph
1 parent 1f4dd2f commit 12665dc

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1 file changed

+128
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1 file changed

+128
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‎CCSPiJ/src/chapter4/Graph.java‎

Lines changed: 128 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,12 @@
11
package chapter4;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import java.util.stream.Collectors;
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import chapter2.GenericSearch;
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import chapter2.GenericSearch.Node;
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// V is the type of the vertices in the Graph
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public class Graph<V> {
@@ -17,14 +22,135 @@ public Graph() {
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public Graph(List<V> vertices) {
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this.vertices = new ArrayList<>(vertices);
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edges = new ArrayList<>();
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for (inti = 0; i < this.vertices.size(); i++) {
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for (Velement : this.vertices) {
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edges.add(new ArrayList<Edge>());
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}
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}
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// Number of vertices
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public int getVertexCount() {
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return vertices.size();
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}
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// Number of edges
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public int getEdgeCount() {
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return edges.stream().mapToInt(al -> al.size()).sum();
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}
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// Add a vertex to the graph and return its index
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public int addVertex(V vertex) {
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vertices.add(vertex);
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edges.add(new ArrayList<>());
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return getVertexCount() - 1;
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}
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// This is an undirected graph, so we always add
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// edges in both directions
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public void addEdge(Edge edge) {
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edges.get(edge.u).add(edge);
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edges.get(edge.v).add(edge.reversed());
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}
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// Add an edge using vertex indices (convenience method)
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public void addEdge(int u, int v) {
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addEdge(new Edge(u, v));
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}
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// Add an edge by looking up vertex indices (convenience method)
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public void addEdge(V first, V second) {
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addEdge(new Edge(indexOf(first), indexOf(second)));
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}
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// Find the vertex at a specific index
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public V vertexAt(int index) {
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return vertices.get(index);
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}
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// Find the index of a vertex in the graph
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public int indexOf(V vertex) {
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return vertices.indexOf(vertex);
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}
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// Find the vertices that a vertex at some index is connected to
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public List<V> neighborsOf(int index) {
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return edges.get(index).stream()
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.map(edge -> vertexAt(edge.v))
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.collect(Collectors.toList());
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}
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// Look up a vertice's index and find its neighbors (convenience method)
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public List<V> neighborsOf(V vertex) {
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return neighborsOf(indexOf(vertex));
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}
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// Return all of the edges associated with a vertex at some index
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public List<Edge> edgesOf(int index) {
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return edges.get(index);
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}
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// Look up the index of a vertex and return its edges (convenience method)
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public List<Edge> edgesOf(V vertex) {
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return edgesOf(indexOf(vertex));
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}
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// Make it easy to pretty-print a Graph
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@Override
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public String toString() {
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StringBuilder sb = new StringBuilder();
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for (int i = 0; i < vertices.size(); i++) {
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sb.append(vertexAt(i).toString());
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sb.append(" -> ");
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sb.append(Arrays.toString(neighborsOf(i).toArray()));
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sb.append(System.lineSeparator());
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}
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return sb.toString();
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}
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// Test basic Graph construction
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public static void main(String[] args) {
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// TODO Auto-generated method stub
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// Represents the 15 largest MSAs in the United States
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Graph<String> cityGraph = new Graph<>(
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List.of("Seattle", "San Francisco", "Los Angeles", "Riverside", "Phoenix", "Chicago", "Boston",
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"New York", "Atlanta", "Miami", "Dallas", "Houston", "Detroit", "Philadelphia", "Washington"));
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cityGraph.addEdge("Seattle", "Chicago");
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cityGraph.addEdge("Seattle", "San Francisco");
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cityGraph.addEdge("San Francisco", "Riverside");
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cityGraph.addEdge("San Francisco", "Los Angeles");
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cityGraph.addEdge("Los Angeles", "Riverside");
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cityGraph.addEdge("Los Angeles", "Phoenix");
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cityGraph.addEdge("Riverside", "Phoenix");
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cityGraph.addEdge("Riverside", "Chicago");
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cityGraph.addEdge("Phoenix", "Dallas");
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cityGraph.addEdge("Phoenix", "Houston");
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cityGraph.addEdge("Dallas", "Chicago");
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cityGraph.addEdge("Dallas", "Atlanta");
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cityGraph.addEdge("Dallas", "Houston");
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cityGraph.addEdge("Houston", "Atlanta");
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cityGraph.addEdge("Houston", "Miami");
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cityGraph.addEdge("Atlanta", "Chicago");
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cityGraph.addEdge("Atlanta", "Washington");
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cityGraph.addEdge("Atlanta", "Miami");
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cityGraph.addEdge("Miami", "Washington");
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cityGraph.addEdge("Chicago", "Detroit");
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cityGraph.addEdge("Detroit", "Boston");
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cityGraph.addEdge("Detroit", "Washington");
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cityGraph.addEdge("Detroit", "New York");
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cityGraph.addEdge("Boston", "New York");
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cityGraph.addEdge("New York", "Philadelphia");
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cityGraph.addEdge("Philadelphia", "Washington");
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System.out.println(cityGraph.toString());
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Node<String> bfsResult = GenericSearch.bfs("Boston",
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v -> v.equals("Miami"),
146+
cityGraph::neighborsOf);
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if (bfsResult == null) {
148+
System.out.println("No solution found using breadth-first search!");
149+
} else {
150+
List<String> path = GenericSearch.nodeToPath(bfsResult);
151+
System.out.println("Path from Boston to Miami:");
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System.out.println(path);
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}
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}
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}

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