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Challenge 208: Trail Traversal

curriculum/challenges/english/blocks/daily-coding-challenges-javascript/698a1a863194f1f4e63f645f.md

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--description--

Given an array of strings representing your trail map, return a string of the moves needed to get to your goal.

The given strings will contain the values:

  • "C": Your current location
  • "G": Your goal
  • "T": Traversable parts of the trail
  • "-": Untraversable parts of the map

Return a string with the moves needed to follow the trail from your location to your goal where:

  • "R" is a move right

  • "D" is a move down

  • "L" is a move left

  • "U" is a move up

  • There will always be a single continuous trail, without any branching, from your current location to your goal.

  • Each trail location will have a maximum of two traversable locations touching it.

For example, given:

js
[
  "-CT--",
  "--T--",
  "--TT-",
  "---T-",
  "---G-"
]

Return "RDDRDD".

--hints--

navigateTrail(["-CT--", "--T--", "--TT-", "---T-", "---G-"]) should return "RDDRDD".

js
assert.equal(navigateTrail(["-CT--", "--T--", "--TT-", "---T-", "---G-"]), "RDDRDD");

navigateTrail(["-----", "--TTG", "--T--", "--T--", "CTT--"]) should return "RRUUURR".

js
assert.equal(navigateTrail(["-----", "--TTG", "--T--", "--T--", "CTT--"]), "RRUUURR");

navigateTrail(["-C----", "TT----", "T-----", "TTTTT-", "----G-"]) should return "DLDDRRRRD".

js
assert.equal(navigateTrail(["-C----", "TT----", "T-----", "TTTTT-", "----G-"]), "DLDDRRRRD");

navigateTrail(["--------", "-CTTT---", "----T---", "---GT---", "--------"]) should return "RRRDDL".

js
assert.equal(navigateTrail(["--------", "-CTTT---", "----T---", "---GT---", "--------"]), "RRRDDL");

navigateTrail(["TTTTTTT-", "T-----T-", "T-----T-", "TTTT--TG", "---C----"]) should return "ULLLUUURRRRRRDDDR".

js
assert.equal(navigateTrail(["TTTTTTT-", "T-----T-", "T-----T-", "TTTT--TG", "---C----"]), "ULLLUUURRRRRRDDDR");

--seed--

--seed-contents--

js
function navigateTrail(map) {

  return map;
}

--solutions--

js
function navigateTrail(map) {
  const rows = map.length;
  const cols = map[0].length;

  const directions = [
    [0, 1, "R"],
    [1, 0, "D"],
    [0, -1, "L"],
    [-1, 0, "U"],
  ];

  let row, col;
  for (let r = 0; r < rows; r++) {
    for (let c = 0; c < cols; c++) {
      if (map[r][c] === "C") {
        row = r;
        col = c;
      }
    }
  }

  let result = "";
  let prev = null;

  while (map[row][col] !== "G") {
    for (let [dr, dc, move] of directions) {
      const newRow = row + dr;
      const newCol = col + dc;

      if (
        newRow >= 0 &&
        newRow < rows &&
        newCol >= 0 &&
        newCol < cols &&
        (map[newRow][newCol] === "T" ||
          map[newRow][newCol] === "G") &&
        (!prev || newRow !== prev[0] || newCol !== prev[1])
      ) {
        result += move;
        prev = [row, col];
        row = newRow;
        col = newCol;
        break;
      }
    }
  }

  return result;
}