Passing a pub
Bloom is not being hyperbolic when he muses, "Good puzzle would be cross Dublin without passing a pub." Indeed, many intrepid walkers and pub dwellers equipped with maps have been defeated by Bloom's puzzle in the nearly 100 years since the publication of Ulysses. In 2011, however, a software developer named Rory McCann used a computer algorithm to thread the maze.
McCann, a UCD computer science graduate, did it by defining borders along the Royal Canal and the Grand Canal (the commonly recognized boundaries of Dublin in Joyce's time), plotting the locations of over a thousand pubs within those borders on a street map, establishing an exclusion zone from the front of every pub defined by a parameter of 35 meters, staking out 15 points along the northern boundary and 15 along the southern one, and writing a program whose task was to find a route from some point on the northern border to some point on the southern one, traveling along city streets and avoiding the exclusion zones.
As soon as McCann published a result, members of his online community wrote to inform him of pubs that he had not included on his map. After several iterations, the computer found a single route from the northwest to the southeast that McCann feels reasonably confident about. Interestingly, although the plotted route avoids every pub on McCann's map, it did manage to pass directly by the Guinness brewery at St. James' Gate.
Reporting on the feat in 2011, the Daily Mail observed, "Particularly likely to come under attack from pedantic Joyce fans is his decision to ignore hotels and restaurants which serve drinks and may even have their own bar inside." McCann acknowledged in that article that "It's a contentious issue. . . . But they are not pubs." The reporter concluded the article by noting, "Others have long since claimed the answer to the riddle was simple: you can cross Dublin not passing any pub by simply going into them."