说明：  A*算法属于一种启发式搜索,它扩展结点的次序类似于广度优先搜索,但不同的是每生成一个子结点需要计算估价函数F,以估算起始结点的约束经过该结点至达目标结点的最佳路径代价 每当扩展结点时,意是在所有待扩展结点中选择具有最小F值的结点做为扩展对象,以便使搜索尽量沿最有希望的方向进行.A*算法只要求产生问题的全部状态空间的部分结点及关系,就可以求解问题了,搜索效率较高
(A* algorithm is a heuristic search, which extended the order of nodes is similar to breadth-first search, but the difference is that each node generates a subset of calculated cost function F, to estimate the initial bound node through the node to reach the target node the best path when the cost of the expansion of nodes, the intention is to be extended in all nodes in the selection of the smallest F value for the expansion of the target node in order to make the search as far as possible along the most promising direction . A* algorithm only requires a problem all part of the state space and the relationship between nodes, we can solve the problem, the search more efficient)