CHAPTER 25 Weighted Graphs and Applications Objectives • To ...

45 for (int k = 0; k < 9; k++)
46 {
47 vector node = getNode(u);
48 if (node[k] == 'H')
49 {
50 int v = getFlippedNode(node, k);
51 int numberOfFlips = getNumberOfFlips(u, v);
52 // Add edge (v, u) for a legal move from node u to node v
53 // with weight numberOfFlips
54 edges.push_back(WeightedEdge(v, u, numberOfFlips));
55 }
56 }
57 }
58
59 return edges;
60 }
61
62 int WeightedNineTailModel::getNumberOfFlips(int u, int v)
63 {
64 vector node1 = getNode(u);
65 vector node2 = getNode(v);
66
67 int count = 0; // Count the number of different cells
68 for (unsigned i = 0; i < node1.size(); i++)
69 if (node1[i] != node2[i]) count++;
70
71 return count;
72 }
73
74 int WeightedNineTailModel::getNumberOfFlips(int u)
75 {
76 return static_cast(tree)->getCost(u);
77 }
78 #endif
WeightedNineTailModel extends NineTailModel to build a WeightedGraph to model the
weighted nine tail problem (line 9). For each node u, the getEdges() function finds a flipped node v
and assigns the number of flips as the weight for edge (u, v) (line 50). The getNumberOfFlips(int
u, int v) function returns the number of flips from node u to node v (lines 62–72). The number of
flips is the number of the different cells between the two nodes (line 69).
The WeightedNineTailModel constructs a WeightedGraph (line 33) and obtains a
ShortestPathTree rooted at the target node 511 (line 36). It then assigns it to tree* (line 36).
tree, of the Tree* type, is a protected data field defined NineTailModel. The functions defined in
NineTailModel use the tree property. Note that ShortestPathTree is a child class of Tree.
42