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extern/stdcxx/4.2.1/examples/tutorial/graph.cpp

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+/**************************************************************************
+ *
+ * graph.cpp - Example of a Graph built from STL's map.
+ *
+ * $Id: graph.cpp 580483 2007-09-28 20:55:52Z sebor $
+ *
+ ***************************************************************************
+ *
+ * Licensed to the Apache Software  Foundation (ASF) under one or more
+ * contributor  license agreements.  See  the NOTICE  file distributed
+ * with  this  work  for  additional information  regarding  copyright
+ * ownership.   The ASF  licenses this  file to  you under  the Apache
+ * License, Version  2.0 (the  "License"); you may  not use  this file
+ * except in  compliance with the License.   You may obtain  a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the  License is distributed on an  "AS IS" BASIS,
+ * WITHOUT  WARRANTIES OR CONDITIONS  OF ANY  KIND, either  express or
+ * implied.   See  the License  for  the  specific language  governing
+ * permissions and limitations under the License.
+ *
+ * Copyright 1994-2006, 2007 Rogue Wave Software, Inc.
+ * 
+ **************************************************************************/
+
+#include <map>
+#include <vector>
+#include <queue>
+#include <iostream>
+#include <string>
+
+#include <examples.h>
+
+typedef std::map<std::string, int>       Distances;
+typedef std::map<std::string, Distances> Cities;
+typedef std::pair<unsigned, std::string> DistancePair;
+
+bool operator< (const DistancePair& lhs, const DistancePair& rhs) {
+    
+    return lhs.first < rhs.first;
+}
+
+
+bool operator> (const DistancePair& lhs, const DistancePair& rhs) {
+    
+    return lhs.first > rhs.first;
+}
+
+
+static void
+shortestDistance (Cities            &city_map,
+                  const std::string &start_city,
+                  Distances         &dist)
+{
+    
+    // Process a priority queue of distances to nodes.
+    std::priority_queue<DistancePair,
+                        std::vector<DistancePair,
+                                    std::allocator<DistancePair> >,
+                        std::greater<DistancePair> > que;
+
+    que.push (DistancePair (0, start_city));
+    
+    while (! que.empty ()) {
+        
+        // Pull nearest city from queue.
+        int distance = que.top ().first;
+        std::string city = que.top ().second;
+        que.pop ();
+
+        // If we haven't seen it already, process it.
+        if (0 == dist.count (city))
+        {
+            // Then add it to shortest distance map.
+            dist[city] = distance;
+
+            // And put values into queue.
+            const Distances& cities = city_map[city];
+            Distances::const_iterator start = cities.begin ();
+            Distances::const_iterator stop  = cities.end ();
+
+            for (; start != stop; ++start) 
+                que.push (DistancePair (distance + (*start).second,
+                                      (*start).first));
+        }
+    }
+}
+
+
+int main () {
+    
+    std::cout << "Graph example program "
+              << " - find shortest path in a directed graph." 
+              << std::endl;
+
+    static const char pendleton[]  = "Pendleton";
+    static const char pensacola[]  = "Pensacola";
+    static const char peoria[]     = "Peoria";
+    static const char phoenix[]    = "Phoenix";
+    static const char pierre[]     = "Pierre";
+    static const char pittsburgh[] = "Pittsburgh";
+    static const char princeton[]  = "Princeton";
+    static const char pueblo[]     = "Pueblo";
+
+    Cities cityMap;
+
+    cityMap[pendleton][phoenix]    = 4;
+    cityMap[pendleton][pueblo]     = 8;
+    cityMap[pensacola][phoenix]    = 5;
+    cityMap[peoria][pittsburgh]    = 5;
+    cityMap[peoria][pueblo]        = 3;
+    cityMap[phoenix][peoria]       = 4;
+    cityMap[phoenix][pittsburgh]   = 10;
+    cityMap[phoenix][pueblo]       = 3;
+    cityMap[pierre][pendleton]     = 2;
+    cityMap[pittsburgh][pensacola] = 4;
+    cityMap[princeton][pittsburgh] = 2;
+    cityMap[pueblo][pierre]        = 3;
+    
+    Distances dist;
+    
+    shortestDistance (cityMap, pierre, dist);
+    Distances::iterator where;
+
+    std::cout << "Find the shortest path from : " 
+              << pierre << '\n';
+
+    for (where = dist.begin (); where != dist.end (); ++where)
+        std::cout << "  Distance to: " << (*where).first << ":"
+                  <<  (*where).second << '\n';
+        
+    std::cout << "End of graph example program" << '\n';
+
+    return 0;
+}