by Nick MacKinnon
Published: 4 December 2016 (link)
Each postcode in Ruritania consists of ten digits, the first three showing the area, the next three showing the town, and the final four showing the house. Just twelve houses have “lucky” postcodes that have no repeated digit and which consist of two three-figure squares followed by a four-figure square. Rudolph lives in such a house and he recently met a girl called Flavia. She only told him that hers was the only house in her area with a lucky postcode, and that her area/town/house numbers were all bigger than his. He has found a postcode satisfying these conditions and sent her a Christmas card, but it has been returned as it was not her postcode.
What is Rudolph’s postcode?