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Commit 0b8db59

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phishman3579
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Cleaned up the path code in the graph to be more readable
git-svn-id: https://java-algorithms-implementation.googlecode.com/svn/trunk@69 032fbc0f-8cab-eb90-e552-f08422b9a96a
1 parent e371ff4 commit 0b8db59

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3 files changed

+23
-44
lines changed

3 files changed

+23
-44
lines changed

‎src/com/jwetherell/algorithms/data_structures/Graph.java

Lines changed: 5 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,6 @@
11
package com.jwetherell.algorithms.data_structures;
22

33
import java.util.ArrayList;
4-
import java.util.Iterator;
54
import java.util.List;
65
import java.util.Set;
76

@@ -241,9 +240,9 @@ public String toString() {
241240
public static class CostPathPair {
242241

243242
private int cost = 0;
244-
private Set<Vertex> path = null;
243+
private Set<Edge> path = null;
245244

246-
public CostPathPair(int cost, Set<Vertex> path) {
245+
public CostPathPair(int cost, Set<Edge> path) {
247246
if (path==null) throw (new NullPointerException("path cannot be NULL."));
248247

249248
this.cost = cost;
@@ -257,21 +256,17 @@ public void setCost(int cost) {
257256
this.cost = cost;
258257
}
259258

260-
public Set<Vertex> getPath() {
259+
public Set<Edge> getPath() {
261260
return path;
262261
}
263262

264263
@Override
265264
public String toString() {
266265
StringBuilder builder = new StringBuilder();
267266
builder.append("Cost = ").append(cost).append("\n");
268-
Iterator<Vertex> iter = path.iterator();
269-
while (iter.hasNext()) {
270-
Vertex v =iter.next();
271-
builder.append(v.getValue());
272-
if (iter.hasNext()) builder.append("->");
267+
for (Edge e : path) {
268+
builder.append("\t").append(e);
273269
}
274-
builder.append("\n");
275270
return builder.toString();
276271
}
277272
}

‎src/com/jwetherell/algorithms/graph/BellmanFord.java

Lines changed: 8 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -20,7 +20,7 @@
2020
public class BellmanFord {
2121

2222
private static Map<Graph.Vertex, Graph.CostVertexPair> costs = null;
23-
private static Map<Graph.Vertex, Set<Graph.Vertex>> paths = null;
23+
private static Map<Graph.Vertex, Set<Graph.Edge>> paths = null;
2424

2525
private BellmanFord() { }
2626

@@ -30,7 +30,7 @@ public static Map<Graph.Vertex, Graph.CostPathPair> getShortestPaths(Graph g, Gr
3030
for (Graph.CostVertexPair pair : costs.values()) {
3131
int cost = pair.getCost();
3232
Graph.Vertex vertex = pair.getVertex();
33-
Set<Graph.Vertex> path = paths.get(vertex);
33+
Set<Graph.Edge> path = paths.get(vertex);
3434
map.put(vertex, new Graph.CostPathPair(cost,path));
3535
}
3636
return map;
@@ -39,9 +39,9 @@ public static Map<Graph.Vertex, Graph.CostPathPair> getShortestPaths(Graph g, Gr
3939
public static Graph.CostPathPair getShortestPath(Graph g, Graph.Vertex start, Graph.Vertex end) {
4040
if (g==null) throw (new NullPointerException("Graph must be non-NULL."));
4141

42-
paths = new TreeMap<Graph.Vertex, Set<Graph.Vertex>>();
42+
paths = new TreeMap<Graph.Vertex, Set<Graph.Edge>>();
4343
for (Graph.Vertex v : g.getVerticies()) {
44-
paths.put(v, new LinkedHashSet<Graph.Vertex>());
44+
paths.put(v, new LinkedHashSet<Graph.Edge>());
4545
}
4646

4747
costs = new TreeMap<Graph.Vertex, Graph.CostVertexPair>();
@@ -73,28 +73,20 @@ public static Graph.CostPathPair getShortestPath(Graph g, Graph.Vertex start, Gr
7373
} else {
7474
// Found a shorter path to a reachable vertex
7575
pair.setCost(cost);
76-
Set<Graph.Vertex> set = paths.get(e.getToVertex());
76+
Set<Graph.Edge> set = paths.get(e.getToVertex());
7777
set.clear();
7878
set.addAll(paths.get(e.getFromVertex()));
79-
set.add(e.getFromVertex());
79+
set.add(e);
8080
}
8181
}
8282
}
8383
}
8484

85-
// Add the end vertex to the Set, just to make it more understandable.
8685
if (end!=null) {
8786
Graph.CostVertexPair pair = costs.get(end);
88-
Set<Graph.Vertex> set = paths.get(end);
89-
set.add(end);
90-
87+
Set<Graph.Edge> set = paths.get(end);
9188
return (new Graph.CostPathPair(pair.getCost(),set));
92-
} else {
93-
for (Graph.Vertex v1 : paths.keySet()) {
94-
Set<Graph.Vertex> v2 = paths.get(v1);
95-
v2.add(v1);
96-
}
97-
return null;
9889
}
90+
return null;
9991
}
10092
}

‎src/com/jwetherell/algorithms/graph/Dijkstra.java

Lines changed: 10 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -23,7 +23,7 @@
2323
public class Dijkstra {
2424

2525
private static Map<Graph.Vertex, Graph.CostVertexPair> costs = null;
26-
private static Map<Graph.Vertex, Set<Graph.Vertex>> paths = null;
26+
private static Map<Graph.Vertex, Set<Graph.Edge>> paths = null;
2727
private static Queue<Graph.CostVertexPair> unvisited = null;
2828

2929
private Dijkstra() { }
@@ -34,7 +34,7 @@ public static Map<Graph.Vertex, Graph.CostPathPair> getShortestPaths(Graph g, Gr
3434
for (Graph.CostVertexPair pair : costs.values()) {
3535
int cost = pair.getCost();
3636
Graph.Vertex vertex = pair.getVertex();
37-
Set<Graph.Vertex> path = paths.get(vertex);
37+
Set<Graph.Edge> path = paths.get(vertex);
3838
map.put(vertex, new Graph.CostPathPair(cost,path));
3939
}
4040
return map;
@@ -47,9 +47,9 @@ public static Graph.CostPathPair getShortestPath(Graph g, Graph.Vertex start, Gr
4747
boolean hasNegativeEdge = checkForNegativeEdges(g.getVerticies());
4848
if (hasNegativeEdge) throw (new IllegalArgumentException("Negative cost Edges are not allowed."));
4949

50-
paths = new TreeMap<Graph.Vertex, Set<Graph.Vertex>>();
50+
paths = new TreeMap<Graph.Vertex, Set<Graph.Edge>>();
5151
for (Graph.Vertex v : g.getVerticies()) {
52-
paths.put(v, new LinkedHashSet<Graph.Vertex>());
52+
paths.put(v, new LinkedHashSet<Graph.Edge>());
5353
}
5454

5555
costs = new TreeMap<Graph.Vertex, Graph.CostVertexPair>();
@@ -71,16 +71,16 @@ public static Graph.CostPathPair getShortestPath(Graph g, Graph.Vertex start, Gr
7171
if (pair.getCost()==Integer.MAX_VALUE) {
7272
// Haven't seen this vertex yet
7373
pair.setCost(cost);
74-
Set<Graph.Vertex> set = paths.get(e.getToVertex());
74+
Set<Graph.Edge> set = paths.get(e.getToVertex());
7575
set.addAll(paths.get(e.getFromVertex()));
76-
set.add(e.getFromVertex());
76+
set.add(e);
7777
} else if (cost<pair.getCost()) {
7878
// Found a shorter path to a reachable vertex
7979
pair.setCost(cost);
80-
Set<Graph.Vertex> set = paths.get(e.getToVertex());
80+
Set<Graph.Edge> set = paths.get(e.getToVertex());
8181
set.clear();
8282
set.addAll(paths.get(e.getFromVertex()));
83-
set.add(e.getFromVertex());
83+
set.add(e);
8484
}
8585
}
8686

@@ -102,20 +102,12 @@ public static Graph.CostPathPair getShortestPath(Graph g, Graph.Vertex start, Gr
102102
}
103103
}
104104

105-
// Add the end vertex to the Set, just to make it more understandable.
106105
if (end!=null) {
107106
Graph.CostVertexPair pair = costs.get(end);
108-
Set<Graph.Vertex> set = paths.get(end);
109-
set.add(end);
110-
107+
Set<Graph.Edge> set = paths.get(end);
111108
return (new Graph.CostPathPair(pair.getCost(),set));
112-
} else {
113-
for (Graph.Vertex v1 : paths.keySet()) {
114-
Set<Graph.Vertex> v2 = paths.get(v1);
115-
v2.add(v1);
116-
}
117-
return null;
118109
}
110+
return null;
119111
}
120112

121113
private static boolean checkForNegativeEdges(List<Graph.Vertex> vertitices) {

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