Solution to the puzzle Cat Walk.

Cat Walk is one of the interesting puzzles of the Melbourne University Puzzle Hunt 2012 competition. This task was part of the second act of the game and was preceded by a short narrative, that continued the plot. In accordance with it, you receive the parcel from your strange companion: a small flash drive is wrapped inside what appears to be a torn page from a children’s puzzle book. You stare long and hard at the puzzle before asking your companion if you had the right answer. He looks back in amazement, quickly plugs the USB drive into his laptop and then happily reports: “This is wonderful! You’ve figured out the password - this is everything that we needed...” As it turned out, the flash drive contained extremely important information, and the solution to the “children's puzzle” was the password to obtain it…

The puzzle itself was below. It was a rectangular maze with colored gates between its parts: gray, red, blue and green. At the bottom of the maze, near the two entrances to it, sat Simon's Cat, who showed with a gesture that he was hungry. The cat's food was at the opposite end of the maze, to which 7 colored exits led.

This puzzle was made by the education officer and later president of the Melbourne University Mathematics and Statistics Society (MUMS) at the time, Giles Adams.

The first step in solving the puzzle was to determine the number of columns in the maze: there were 26, which corresponds to the number of letters in the English alphabet. Thus, each column could be assigned a letter corresponding to it by number. Then you should pay attention to the colors of the gates inside the maze. You could try to go through the maze using gates of only one color. This was possible to do only for one of the colors - for gray - and only in a single way (if you never move along the path already taken).

A message could be extracted from this passage. To do this, whenever the path ran through a gray vertical gate, a letter corresponding to the column number for this gate had to be added to the message. The result was REDBLUETHENGREENPATH or RED, BLUE THEN GREEN PATH. Thus, the hint suggested going through the maze one more time, but now alternating the gates of red, blue and green. Again there was only one way to do this.

After successful completion you could receive another message in the same way. To do this, whenever the path ran through a vertical colored gate, the message had to be supplemented with the corresponding letter. The result was BLACKANDWHITECATFOOT or BLACK AND WHITE CAT FOOT. This strange phrase is a literal translation of the Latin term, that refers to the animal species Giant panda (Ailuropoda melanoleuca). Thus, the answer to the task was GIANT PANDA.

An interesting challenge for this puzzle is to write a program, that can automatically find the required paths in the maze and extract messages from them. Here you can find the code for such a program in Python.

Some additional information about the puzzle could be found in the notes for it. There were 3 common guesses given by players: GIANT PANDA (77 times), PANDA (19 times) and BLACK AND WHITE CAT FOOT (11 times). The Background section describes how the task was created.

“This puzzle emerged from a straightforward concept of a maze spelling an answer phrase via either absolute or relative displacements of its solution path. It was later extended to allow for a two-stage process that was intended to be more fun to solve (and which was intentionally made more difficult via lots of long, dead-end branchings in the Red-Blue-Green gateways) but presented no greater difficulty to construct due to the mutual exclusivity of the colouring.

Various second stage answer phrase were floated (i.e. EATS SHOOTS AND LEAVES, SPECIFICALLY PO NOT SHIFU, BEAR APPEARING ON WWF LOGO, etc) in an attempt to differentiate the answer GIANT PANDA from just PANDA [the answer GIANT PANDA was selected in advance for that year's meta-puzzle], though BLACK AND WHITE CAT FOOT was ultimately chosen to coincide with the prevalence of colours in the maze.”