001 package aima.search.framework;
002
003 /**
004 * Artificial Intelligence A Modern Approach (2nd Edition): Figure 3.7, page 70.
005 * <code>
006 * function TREE-SEARCH(problem, strategy) returns a solution, or failure
007 * initialize the search tree using the initial state of problem
008 * loop do
009 * if there are no candidates for expansion then return failure
010 * choose a leaf node for expansion according to strategy
011 * if the node contains a goal state then return the corresponding solution
012 * else expand the node and add the resulting nodes to the search tree.
013 * </code>
014 * Figure 3.7 An informal description of the general tree-search algorithm.
015 *
016 *
017 * Artificial Intelligence A Modern Approach (2nd Edition): Figure 3.9, page 72.
018 * <code>
019 * function TREE-SEARCH(problem, fringe) returns a solution, or failure
020 *
021 * fringe <- INSERT(MAKE-NODE(INITIAL-STATE[problem]), fringe)
022 * loop do
023 * if EMPTY?(fringe) then return failure
024 * node <- REMOVE-FIRST(fringe)
025 * if GOAL-TEST[problem] applied to STATE[node] succeeds
026 * the return SOLUTION(node)
027 * fringe <- INSERT-ALL(EXPAND(node, problem), fringe)
028 * ---------------------------------------------------------------------
029 * function EXPAND(node, problem) returns a set of nodes
030 *
031 * successors <- empty set
032 * for each <action, result> in SUCCESSOR-FN[problem](STATE[node]) do
033 * s <- a new NODE
034 * STATE[s] <- result
035 * PARENT-NODE[s] <- node
036 * ACTION[s] <- action
037 * PATH-COST[s] <- PATH-COST[node] + STEP-COSTS(STATE[node], action, result)
038 * DEPTH[s] <- DEPTH[node] + 1
039 * add s to successor
040 * return successors
041 * </code>
042 * Figure 3.9 The general tree-search algorithm. (Note that the fringe argument must be an
043 * empty queue, and the type of the queue will affect the order of the search.) The SOLUTION
044 * function returns the sequence of actions obtained by following parent pointers back to the
045 * root.
046 */
047
048 /**
049 * @author Ravi Mohan
050 *
051 */
052
053 public class TreeSearch extends QueueSearch {
054
055 @Override
056 public void addExpandedNodesToFringe(NodeStore fringe, Node node,
057 Problem problem) {
058 fringe.add(expandNode(node, problem));
059 }
060
061 }