一个星型搜索算法
本文关键字:星型 搜索算法 一个 | 更新日期: 2023-09-27 18:10:01
这里我有一个关于a星搜索算法的查询。我正在制作所谓的8块拼图。这是一个有9个位置(1个为空)的游戏,你必须按照正确的顺序排列瓷砖以达到目标位置。
我只需要验证我是否正确地编写了算法,以便我可以在代码的其他地方寻找问题。
我个人认为这个算法是正确的,因为它能够解决我创建的第一个预先设置的谜题,只需要一次移动就可以到达目标位置。然而,它无法解决需要更多移动的谜题。
我试过用三种不同的方法来解决这个问题,但都带来了同样的问题。
尝试1:
while (openList.Count() > 0)
{
PuzzleNode currentNode;
var orderedOpenList = openList.OrderBy(PuzzleNode => PuzzleNode.getPathCost());
currentNode = orderedOpenList.First();
if (compare(currentNode.getPuzzle(), goalArray) == true)
{
//openList.RemoveAt(0); //POLL
break;
// otherwise push currentNode onto closedList & remove from openList
}
else
{
openList.Remove(currentNode);
closedList.Add(currentNode);
}
//generate all the neighbor nodes
generateSuccessors(currentNode, tempList);
for (int i = 0; i < tempList.Count(); i++)
{
PuzzleNode tempNode = tempList[i];
//skip the node if it's in the closed list
if (closedList.Contains(tempNode))
{
continue;
}//end if
//We need to ensure that the G we have seen here is the shortest one
int gScore = currentNode.getG() + 1;
if (!openList.Contains(tempNode) || gScore < tempNode.getG())
{
tempNode.setParentNode(currentNode);
tempNode.setH(tempNode.calcH(currentHueristic, tempNode.getPuzzle(), goalArray));
tempNode.setG(gScore);
tempNode.updatePathCost();
if (!openList.Contains(tempNode))
{
openList.Add(tempNode);
}//end if
}//end if
}//end for
}//end while
尝试2:
while (openList.Count() > 0)
{
PuzzleNode currentNode = GetBestNodeFromOpenList(openList);
openList.Remove(currentNode);
closedList.Add(currentNode);
generateSuccessors(currentNode, tempList);
foreach (PuzzleNode successorNode in tempList)
{
if (compare(successorNode.getPuzzle(), goalArray) == true)
{
//goto thebreak;
return successorNode;
}
successorNode.setG(currentNode.getG() + 1);
successorNode.setH(successorNode.calcH(currentHueristic, successorNode.getPuzzle(), goalArray));
successorNode.updatePathCost();
if (OpenListHasBetterNode(successorNode, openList))
continue;
openList.Add(successorNode);
}
}//end while
private static PuzzleNode GetBestNodeFromOpenList(IEnumerable<PuzzleNode> openList)
{
return openList.OrderBy(n => n.getPathCost()).First();
}
private static bool OpenListHasBetterNode(PuzzleNode successor, IEnumerable<PuzzleNode> list)
{
return list.FirstOrDefault(n => n.getG().Equals(successor.getG())
&& n.getPathCost() < successor.getPathCost()) != null;
}
尝试2是我在网上找到的一个算法的修改:解决8个难题
然而,我尽我最大的努力遵循维基百科上的伪代码:
function A*(start,goal)
closedset := the empty set // The set of nodes already evaluated.
openset := {start} // The set of tentative nodes to be evaluated, initially containing the start node
came_from := the empty map // The map of navigated nodes.
g_score[start] := 0 // Cost from start along best known path.
// Estimated total cost from start to goal through y.
f_score[start] := g_score[start] + heuristic_cost_estimate(start, goal)
while openset is not empty
current := the node in openset having the lowest f_score[] value
if current = goal
return reconstruct_path(came_from, goal)
remove current from openset
add current to closedset
for each neighbor in neighbor_nodes(current)
tentative_g_score := g_score[current] + dist_between(current,neighbor)
if neighbor in closedset
if tentative_g_score >= g_score[neighbor]
continue
if neighbor not in openset or tentative_g_score < g_score[neighbor]
came_from[neighbor] := current
g_score[neighbor] := tentative_g_score
f_score[neighbor] := g_score[neighbor] + heuristic_cost_estimate(neighbor, goal)
if neighbor not in openset
add neighbor to openset
我问你是否能找到一个问题,因为我很困惑,为什么它只适用于一个谜题。仅将这些谜题分开,是解决到目标状态所需的移动量。
我已经调试了几个小时了,我就是看不到它,我也看不出我的代码中的其他地方可能有问题。我只是想问,你觉得这样对吗?
任何问题一定要问,我会尽可能提供更多信息!提前感谢!
注意:我使用CustomPriorityQueue类(由itowlson编写),您可以在这里找到
这里我基本上使用了PriorityQueue它会按照启发式值来排列问题状态
下面是一个简单的c#中的a *模板,它说明了a *搜索是如何工作的:
void enqueueAll(CustomPriorityQueue<PuzzleNode> a, ArrayList<PuzzleNode> b)
{
foreach(PuzzleNode c in b) a.enqueue(c, h(c));
}
// A* heuritic: h = f + g ; h <= h*
int h(PuzzleNode n);
// returns TRUE if n is a solution
bool isSolution(PuzzleNode n);
// expand n into list of neighbors
ArrayList<PuzzleNode> expand(PuzzleNode n);
PuzzleNode Astar(PuzzleNode startPoint)
{
CustomPriorityQueue list = new CustomPriorityQueue<PuzzleNode>();
PuzzleNode current = null;
list.enqueue(startPoint, h(startPoint));
while (list.size() > 0)
{
current = list.dequeue();
if (isSolution(current))
{
return current;
}
enqueueAll(list, expand(current));
}
}
希望能有所帮助