Code Golf: Ghost Leg

code-golf, language-agnostic, random, rosetta-stone

Solution

JavaScript: 169 158 148 141 127 125 123 122 Characters

Minified and Golfed:

function g(n,s){for(l=s.split('\n'),n*=2;k=l.shift();)for(j=3;j;)n+=k[n-3]==(c=--j-1?'=':'-')?-2:k[n-1]==c?2:0;return n/2}

Readable Version:

function g(n, str) {
   var c, i, j;
   var lines = str.split('\n');
   n = (n * 2) - 2;

   for (i = 0; i < lines.length; i++) {
      for (j = 0; j < 3; j++) {
         c = (j == 1) ? '-' : '=';

         if (lines[i].charAt(n-1) == c) n-=2;          // Move left
         else if (lines[i].charAt(n+1) == c) n+=2;     // Move right
      }
   }

   return 1+n/2;
}

Explanation:

- `str` is split into an array of lines.

- `n` is scaled to cover the number of characters in each line, starting from 0.

- Iterate three times over each line: one time for each layer. Imagine each line is divided into 3 layers: The top and bottom layers are where the legs of the of the `=` sign are attached. The middle layer is for the legs of the `-` signs.

- Move `n` either left or right according to the adjacent signs. There is only one possible move for every layer of each line. Therefore `n` could move up to 3 times in a line.

- Return `n`, normalized to start from 1 to the number of vertical lines.

Test Cases:

var ghostLegs = [];

ghostLegs[0] = "|-| |=|-|=|\n" +
               "| |-| | |-|\n" +
               "|=| |-| | |\n" +
               "| | |-|=|-|";

ghostLegs[1] = "| | | | | | | |\n" +
               "|-| |=| | | | |\n" +
               "|-| | |-| |=| |\n" +
               "| |-| |-| | |-|";

ghostLegs[2] = "| | |=| |\n" +
               "|-| |-| |\n" +
               "| |-| | |";

ghostLegs[3] = "|=|-|";

for (var m = 0; m < ghostLegs.length; m++) {
   console.log('\nTest: ' + (m + 1) + '\n');

   for (var n = 1; n <= (ghostLegs[m].split('\n')[0].length / 2) + 1; n++) {
      console.log(n + ':' + g(n, ghostLegs[m]));
   }
}

Results:

Test: 1
1:6
2:1
3:3
4:5
5:4
6:2

Test: 2
1:1
2:3
3:2
4:4
5:5
6:6
7:8
8:7

Test: 3
1:3
2:1
3:4
4:2
5:5

Test: 4
1:3
2:2
3:1

Problem

Original source