August 2017
Intermediate to advanced
360 pages
8h 35m
Chinese
Content preview from 算法技术手册（原书第2 版）
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AI
寻路
｜
185
AI
寻路
图 7-15：八数码问题的深度优先搜索树
7.7.3 解决方案
深度优先搜索
在栈中存储一系列
开放
（例如还未被访问）棋局状态，每次从中取出一个
进行处理。在例
7-6
的实现中，闭集的结构是一个散列表，这个结构可以高效地查询一
个棋局状态是否已经访问，它使用的散列函数是根据
INode
对象来计算键值。
每个棋局状态都有一个称为
DepthTransition
的引用，用于记录到达这个状态的走法、
之前状态以及从最初位置开始到此的深度。该算法会多次复制一个棋局状态，用来尝试
各种走法。一旦确定找到的某个结点就是目标状态，搜索终止（这个条件也同样适用于
广度优先搜索
）。
例
7-6
：深度优先搜索实现
public Solution search(INode initial, INode goal) {
//
如果初始状态就是目标解，则直接返回。
if (initial.equals(goal)) { return new Solution(initial, goal); }
INodeSet open = StateStorageFactory.create(OpenStateFactory.STACK);
open.insert(initial.copy());
//
已经访问过此状态。
INodeSet closed = StateStorageFactory.create(OpenStateFactory.HASH);
while (!open.isEmpty()) ...
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