public static GeographyStrategyInfo FindStrategy(AdjacentMap pDirectedGraph, string pStartNode)
{
GeographyStrategyInfo geographyStrategyInfo = FindStrategy(pDirectedGraph, pStartNode, true);
return(geographyStrategyInfo.FoundStrategy
? geographyStrategyInfo
: new GeographyStrategyInfo(false, new List <List <string> >()));
}
private static GeographyStrategyInfo FindStrategy(AdjacentMap pDirectedGraph, string pStartNode, bool pPlayer1Round)
{
GeographyStrategyInfo strategyInfo;
//1. Measure the out-degree of node nstart.If this degree is 0, then return reject, because there are no moves available for player one.
int nodeOutDegree = pDirectedGraph[pStartNode].Count;
if (nodeOutDegree == 0)
{
// no moves possible
strategyInfo = new GeographyStrategyInfo(false, new List <List <string> >()
{
new List <string>()
{
pStartNode
}
});
}
else
{
//2. Construct a list of all nodes reachable from nstart by one edge: n1, n2, ..., ni.
List <string> nextReachableNodes = pDirectedGraph[pStartNode];
//3. Remove nstart and all edges connected to it from G to form G1.
AdjacentMap graph1 = new AdjacentMap(pDirectedGraph);
graph1.Remove(pStartNode);
List <string> keys = new List <string>(graph1.Keys);
foreach (string key in keys)
{
List <string> neighbors = graph1[key];
if (neighbors.Contains(pStartNode))
{
List <string> newNeighbors = neighbors.ToList();
newNeighbors.Remove(pStartNode);
graph1[key] = newNeighbors;
}
}
//4. For each node nj in the list n1, ..., ni, call M(< G1, nj >).
bool foundStrategy = true;
List <List <string> > tempStrategies = new List <List <string> >();
foreach (string nextReachableNode in nextReachableNodes)
{
var currentNodeStrategyInfo = FindStrategy(graph1, nextReachableNode, !pPlayer1Round);
foundStrategy = foundStrategy && currentNodeStrategyInfo.FoundStrategy;
if (!currentNodeStrategyInfo.FoundStrategy && pPlayer1Round || currentNodeStrategyInfo.FoundStrategy && !pPlayer1Round)
{
tempStrategies.AddRange(currentNodeStrategyInfo.Strategies);
}
}
foreach (var strategy in tempStrategies)
{
strategy.Insert(0, pStartNode);
}
//5. If all of these calls return accept, then no matter which decision P1 makes, P2 has a strategy to win, so return reject. Otherwise(if one of the calls returns reject) P1 has a choice that will deny any successful strategies for P2, so return accept.
strategyInfo = new GeographyStrategyInfo(!foundStrategy, tempStrategies);
}
return(strategyInfo);
}
