   Pruning a BFS Tree
  Hey all,I'm looking into methods to prune a breadth-first-search tree for duplicate nodes but am having trouble googling methods and tutorials.Can anyone help me get started?Thanks,   
  Can you explain what you want to do in more words?BFS usually refers to the way you walk over a tree, not the tree itself.  You mean a tree ordered in a manner such that a BF iteration will get the elements in order?  How balanced is it?  Is that the kind of thing you are trying to decide upon - keeping it balanced in some sense?;  Well I'm building the tree to solve a puzzle, children nodes represent the next possible states.  What I'd like is to not have redundant states in the tree so as to not waste time and space.   ;  If there are discrete nodes in memory that form the graph you're searching, and you can store data at those nodes, simply store a bool visited value to check whether it's been expanded before. Otherwise, use a hash-table to store all the states you've already visited. This approach is known as a "transposition table".   ;  Thank you much, Sneftel.  That got me on my way.   