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Question

You have a 50 by 50 character array. Each cell has an arrow pointing in any one of four directions. No cell is empty. On entering a cell, you must exit it in the direction specified by the arrow. The arrow may also point in the same direction you came from, resulting in a dead end.

You may start from any cell on the outermost border of the maze and find a path that takes you in the maze, and causes you to exit at some other cell. Input will be given as an array containing <, >, ^ and v. Output will be a single digit (Boolean, integer or character, anything will do) as 0 (indicating that the task is impossible) or 1 (indicating that you have achieved the task).

Example (actual array will be bigger than this)

^ v < > > < v < v > v ^

Output will be 

1
as you can enter from the < on the right, which will cause you to exit from the bottom v by the path "< v v"

The task is to write the shortest possible code that will receive the maze as input, and determine where there exists a path in it as specified in the rules and output a single digit 0 or 1

Outputing TRUE and FALSE instead of actual digits is also allowed.

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    \$\begingroup\$ It would be nice to have some actual test cases to work with \$\endgroup\$ Commented Oct 31, 2015 at 6:44
  • \$\begingroup\$ Is the input a one dimensional array or a two dimensional? And can you only enter on the right by a < or can you also enter by a ^ ? \$\endgroup\$ Commented Oct 31, 2015 at 8:54
  • \$\begingroup\$ @bobbel Input can be given as a 1 or a 2 dimensional array, whichever is required for a shorter code. Even arrows can be entered as 1 2 3 4 instead of < > ^ v if that can shorten the code. And yes, you can enter via the ^ also. \$\endgroup\$ Commented Oct 31, 2015 at 10:29
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    \$\begingroup\$ The likelihood that a random, 50 by 50, array will not have a solution is just about 0. It would be better if you required that the solution have at least a certain number of steps or that the user specified the solution path. \$\endgroup\$ Commented Oct 31, 2015 at 16:44
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    \$\begingroup\$ This should have been called "An arrow escape"... Still pondering a solution. \$\endgroup\$ Commented Nov 3, 2015 at 20:09

1 Answer 1

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CJam, 89 81 bytes

q~"><v^":A2/{f{\*}z}/sA[1W52-52]er:T,,{[52md]51f%0e=1=},:E{[2704{__T=+}*]\-E&},,g

Try it online in the <>vv^<<^vvvv>v<>^<>>^<^>>>v>^vv><^v>v>>^v^v^" ">v>>>><^><>vv<>^<<>^v>v^>>>^>>>^><<" "^v^^>^^>vv^^^>vv>^^^<^^>>^^<^>^vv<<<>^>^^v>>v" "v>^v<><><><><^><>v>>v<>>v>v>><^^^<>>vv><^<>>>>^<<>^vvvv^^>^vv<>^<^<>^<>>v^^>^^><^v" "v^^<^><v^>><>><>>vv<^^^<^>vv^>>><^^>^<>^v>v^v>^^^vv>^vvv<>><><>>><^^^v^^<^" "^v<^<^^<<><>v^^^^^>vv<>v>^v>^v^^v<^^^^v^^>v>v^>>vvv>>^^^vv>^" "^^vv<>v<v^^vvvv<>>v>>^<^^^>>" "<<vvv^<<>vv>v^v<>^^^>>>>v" "v>v>^>^^v^<<<^>>v>v^<^>v^><^v^><<^vv^<^^v^^^^^<" "v^<<^>^<^^v^><>>^<<<^v>^v>^<^^>v^<^^v^<><<>^<><>>>v^<>v>^<^v<>><<>>v>^><>^>vv" "v^^v><^<>v^>^^><<^><^<^^^^>>v^^^>v>v" "vv^^v^^^<>^^^<<>>>^vvv^^>v>vv><>^<><>^v>>>^" ">^^v<>>>^v>>vv>^^>><<<^<><>^v<^vv>^v^>v<" ">>>^<^vvv>^^^>>vv>>v^v^<><>><>^" ">^>vv^<><>v<^^v^<^<<^v>v<<^<><>vv>^v^<<^v^<^^v^>><<^>>>^>>^vv^v>v>^^>v" "<>^v><^^<^v^>v>v>^>v^^^v^>>^<<<><^<<^vv><^v>>v<>^>^<<^vv>v" "^vv><>vv>v>>><^^v>>>^^<>v^vvv^v>^><^>vvv>v" "<^v><^v<<><^vv^^vv<^v>^>^><>v^<><><<<<^v^v><>v<>^><>>>^^<>vv>v" "v>vv<>^v<^><>vv><>^>v<^>>^<>>v<>>^^v^^<>^v^" "^>^^v<>^vv^>>vvv>^^<^>v>>v<>>v^>v>^v>" "v<>>>^<><^<>v^<<<<^<vv^v<^v^^<>^v>><>^>" "<v>^><^^><>vvvvv>>v<>^>^<<^vv^<<^v<<>>^>v>" "vvv>vvvv>><v>vv^^<^^<><^^<v<^<<^vvvv" "v<>vv<>>v^^<>>v^>v^^v>v>>vv^>v^<>>^<>^>^<^>>^>>>v^>>^^><^^<<>^^>><^v^>>vvv>^>><><^<^v><>>>v^<>><>^><<>>^>v^v<^^^v<>>v>vvv>>>" "<<>>>^^^>^v>>vv>v^v^<<><v><^vv<>>^v<>>^<>^><<^>^^>><>^>^v" "^<^<^^v^v<><>v><>v^^v><^^>v>^v>v>v^v<<<>^^^<" ">^<<^^^vv^v>v<^^^vv^^>v>>^>v<><>v<<>>>^>><^<<>^" "^<^v>v<<>v<^^>v^<>v^<>><<<^>v>>><^>><<^<^><<^^>v>^v<>v<^v^^v>><><^v" ">^<^v>^v><><^<^>><^v><<^>^><^<>>^^^^v>^v" "^vvv<^<v>v<^vv<<>>^<>v^^^^>v>v^^>v^><" "v^>>^<^v>^>^^>v>>v>^^v>v>v^^<^>>^<<^^v" "v^^<^^<^v^^<><>>v>^>v<>>v<^<>v>^>^>^<^^v><>^" "<<<<<<><<^v<^v^>vv>v><>v>v>vv^^<<>>v^^vvvv" ">^v<<^<<^<^^^^>>><<<v>^v^>vv>>vv<^v^<<^v^<<>>v>^><>v>^>v^>^v<>v>vv>>>>^<>^^>v<><>^>^<^v<^v^^<>v><>v^<" ">v>v<<><^^<>^>^>>>v<<>>^<>><>>>>^v>v>" "vv^v>v>vv^^>^<^>^^v^v<^^vvv^<<^v>^v<>v^^" "v<^^^^v>>><>^<^^>vv<><^^><><^vv"]" rel="nofollow">CJam interpreter.

How it works

q~ e# Read and evaluate all input. This pushes an array of strings. "><v^":A e# Push that string and save it in A. 2/ e# Split it into ["><" "v^"]. { e# For each chunk: f{ e# For each input string, push the string and the chunk; then: \* e# Join the chunk, using the string as separator. } e# z e# Transpose rows and columns. }/ e# s e# Flatten the resulting array of strings. A e# Push "><v^". [1W52-52] e# Push [1 -1 52 -52]. er e# Perform transliteration. :T e# Save the result in T. ,, e# Push [0 ... 2703]. { e# Filter; for each integer I in [0 ... 2703]: [52md] e# Push [I/52 I%52]. 51f% e# Take both integers modulo 51 to map 51 to 0. 0e= e# Count the number of resulting zeroes. 1= e# Check if the count is 1. }, e# If it is, keep I. :E e# Save the filtered array in E. { e# For each integer I in E: [2704{ e# Do 2704 times: __ e# Push two copies of the integer on the stack. T= e# Select the corresponding element from T. + e# Add it to the first copy. }*] e# Collect all results in an array. \- e# Remove I from that array. E& e# Intersect with E. }, e# If the intersection is non-empty, keep the integer. ,g e# Push the sign of the length of the filtered array.
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