 The principal difficulty was that , for many problems , the number of possible paths through the " maze " was simply astronomical ( a situation known as a " combinatorial explosion " ) . Researchers would reduce the search space by using heuristics or " rules of thumb " that would eliminate those paths that were unlikely to lead to a solution . 
 The principal difficulty was that , for many problems , the number of possible paths through the " maze " was simply astronomical ( a situation known as a " combinatorial explosion " ) . Researchers would reduce the search space by using heuristics or " rules of thumb " <a href='null_relcl' title='1'><mark>that</mark></a>would eliminate those paths <a href='null_relcl' title='2'><mark>that</mark></a><a href='uninflect' title='3'><mark>were</mark></a> unlikely to lead to a solution . 
Da principal difficulty was that , for many problems , the number of possible paths thru tda" maze " was simply astronomical ( a shyt known as a " combinatorial explosion " ) . Researchers would reduce the search space by using heuristics or " rules of thumb " would eliminate those paths was unlikely to lead to a solution .