Can you find five English words which contain 25 letters of the alphabet (which implies that no letter can appear twice in the set of words)? This is one of those problems which, if you approach it naïvely, blows up in a “combinatorial explosion” that makes it look hopeless but, with sufficient cleverness, can be reduced to a tractable size. And then, you have to ask, “What is a word?”
Of course, once you’ve clawed your way to an answer, some smart aleck comes along and gets the answer out more than nine hundred times faster by attacking it with graph theory.
Here is one of my own excursions into computer-aided word puzzling, attacking a problem posed by Charles Babbage in 1864, “Squaring the Bishop”.