Kata Task

You are given a grid, which always includes exactly two end-points indicated by X

You simply need to return true/false if you can detect a one and only one "valid" line joining those points.

A line can have the following characters :

• - = left / right
• | = up / down
• + = corner

Rules for valid lines

• The most basic kind of valid line is when the end-points are already adjacent

  X
  X
  

  XX
  

• The corner character (+) must be used for all corners (but only for corners).
• If you find yourself at a corner then you must turn.
• It must be possible to follow the line with no ambiguity (lookahead of just one step, and never treading on the same spot twice).
• The line may take any path between the two points.
• Sometimes a line may be valid in one direction but not the other. Such a line is still considered valid.
• Every line "character" found in the grid must be part of the line. If extras are found then the line is not valid.

Examples

Good lines

X---------X

X
|
|
X

   +--------+
X--+        +--+
               |
               X

   +-------------+
   |             |
X--+      X------+    

   +-------+
   |      +++---+
X--+      +-+   X

Bad lines

X-----|----X

X
|
+
X

   |--------+
X---        ---+
               |
               X

   +------ 
   |              
X--+      X  

      +------+
      |      |
X-----+------+
      |
      X

Hint

Imagine yourself walking a path where you can only see your very next step. Can you know which step you must take, or not?