public int CompareTo(Node other)
{
int compare = EstimatedTotalCost.CompareTo(other.EstimatedTotalCost);
if (compare == 0)
{
compare = HeuristicCost.CompareTo(other.HeuristicCost);
}
return(-compare);
}
/// <summary>
/// Finds the path in some problem space from a starting state until a goal condition is satified. <para/>
/// A common application of a heuristic search is implementing path finding.
/// </summary>
/// <remarks>
/// This search implements the famous A* algorithm.
/// </remarks>
/// <typeparam name="T">Type of the state elements.</typeparam>
/// <param name="start">Starting state</param>
/// <param name="goalCondition">Search predicate</param>
/// <param name="getSuccessors">Returns sucessors</param>
/// <param name="cost">Cost function between two states.</param>
/// <param name="heuristic">Estimate cost between state and goal state.</param>
/// <returns>A sequence of states from start (inclusive) to goal (inclusive).</returns>
public static IReadOnlyList <T> HeuristicSearch <T>(T start, Func <T, bool> goalCondition, Func <T, IEnumerable <T> > getSuccessors, ActualCost <T> cost, HeuristicCost <T> heuristic)
{
//
var nodes = new Dictionary <T, Node <T> >();
//
var frontier = new Heap <Node <T> >
{
new Node <T>(start)
{
State = start,
FScore = heuristic(start),
GScore = 0,
}
};
Node <T> GetNode(T state)
{
if (!nodes.TryGetValue(state, out var node))
{
node = new Node <T>(state);
nodes[state] = node;
}
return(node);
}
/// <summary>
/// Finds the path in some problem space from a starting state until a goal state has been reached. <para/>
/// A common application of a heuristic search is implementing path finding.
/// </summary>
/// <remarks>
/// This search implements the famous A* algorithm.
/// </remarks>
/// <typeparam name="T">Type of the state elements.</typeparam>
/// <param name="start">Starting state</param>
/// <param name="goal">Terminating state.</param>
/// <param name="getSuccessors">Returns sucessors</param>
/// <param name="cost">Cost function between two states.</param>
/// <param name="heuristic">Estimate cost between state and goal state.</param>
/// <returns>A sequence of states from start (inclusive) to goal (inclusive).</returns>
public static IReadOnlyList <T> HeuristicSearch <T>(T start, T goal, Func <T, IEnumerable <T> > getSuccessors, ActualCost <T> cost, HeuristicCost <T> heuristic)
{
return(HeuristicSearch(start, x => Equals(x, goal), getSuccessors, cost, heuristic));
}
