public PDAConfiguration checkStackAndCreateNewConfig(PDAConfiguration currentConfig, Queue <char> newWord, Connection transition)
{
Stack <char> newStack = new Stack <char>(new Stack <char>(currentConfig.Stack));
Node newNode = transition.ToNode;
if (currentConfig.Stack.Count > 0)
{
if (transition.PopStack == currentConfig.Stack.Peek())
{
newStack.Pop();
if (transition.PushStack != '_' && transition.PushStack != '\0')
{
newStack.Push(transition.PushStack);
}
return(new PDAConfiguration(newStack, newNode, newWord, currentConfig.Depth + 1));
}
}
if (transition.PopStack == '_')
{
if (transition.PushStack != '_' && transition.PushStack != '\0')
{
newStack.Push(transition.PushStack);
}
return(new PDAConfiguration(newStack, newNode, newWord, currentConfig.Depth + 1));
}
else if (transition.PopStack == '\0')
{
return(new PDAConfiguration(newStack, newNode, newWord, currentConfig.Depth + 1));
}
return(null);
}
public bool wordAcceptancePDA(char[] word)
{
Queue <PDAConfiguration> configurations = new Queue <PDAConfiguration>();
configurations.Enqueue(new PDAConfiguration(new Stack <char>(), automata.nodes[0], new Queue <char>(word), 0));
HashSet <string> oldConfigs = new HashSet <string>();
while (configurations.Count != 0)
{
PDAConfiguration configuration = configurations.Dequeue();
if (configuration.Word.Count == 0 & configuration.Stack.Count == 0 && configuration.Node.Final)
{
return(true);
}
foreach (Connection trans in configuration.Node.Connections)
{
PDAConfiguration newConfig = checkTransitionAndCreateNewConfig(configuration, trans);
if (newConfig != null && newConfig.Depth < 50)
{
string newConfigHashString = newConfig.CreateHashString();
if (!oldConfigs.Contains(newConfigHashString))
{
configurations.Enqueue(newConfig);
oldConfigs.Add(newConfigHashString);
}
}
}
//outcomment this for big performence increase
configuration.print();
}
return(false);
}
public PDAConfiguration checkTransitionAndCreateNewConfig(PDAConfiguration currentConfig, Connection transition)
{
Queue <char> newWord = new Queue <char>(currentConfig.Word);
if (currentConfig.Word.Count > 0)
{
if (transition.Symbol == currentConfig.Word.Peek())
{
newWord.Dequeue();
return(checkStackAndCreateNewConfig(currentConfig, newWord, transition));
}
}
if (transition.Symbol == '_')
{
return(checkStackAndCreateNewConfig(currentConfig, newWord, transition));
}
return(null);
}
