James Joyce’s novel Ulysses first appeared as a serial from March 1918 to December 1920. The primary character, Leopold Bloom, makes a seemingly-offhanded remark that spun into one of history’s most intriguing brain teasers. It would take nearly a century before the solution to that riddle would be solved.

The riddle was sparked by Bloom’s musing, “Good puzzle would be cross Dublin without passing a pub.” Visitors to Dublin have pondered this and attempted to solve the puzzle. All attempts have been frustrated muses Leopold Bloom in James Joyce’s classic novel Ulysses. It’s a conundrum that has intrigued literary visitors to the city for years and, until now, frustrated them.

Enter one software developer by the name of Rory McCann. He was determined to solve the elusive brain teaser with the help of the latest technology. Using OpenStreetMap, an open source online map program, he identified the locations of the more than 1,000 pubs within the city limits of Dublin. He then developed an algorithm to plot a path through the city that remains at least 35 meters (115 feet) from each of them.

McCann thought he had solved the problem in 2011. Only when he attempted to navigate the winding path did he discover many street-side ale vendors that had not made it into his calculations. Three years later, after being confident he had identified all places that could possibly be classified as a pub — including hotels that serve alcohol — he ran his algorithm again. The computer took about fifteen minutes to calculate the results, but when it finished, McCann had the answer to Bloom’s elusive puzzle.

Rory McCann’s computer-generated solution to a 100-year-old brain teaser.

Read about more interesting brain teasers.

Read more fun facts about Ireland.