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Challenge 208: Trail Traversal

curriculum/challenges/english/blocks/daily-coding-challenges-python/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--

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

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(navigate_trail(["-CT--", "--T--", "--TT-", "---T-", "---G-"]), "RDDRDD")`)
}})

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

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(navigate_trail(["-----", "--TTG", "--T--", "--T--", "CTT--"]), "RRUUURR")`)
}})

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

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(navigate_trail(["-C----", "TT----", "T-----", "TTTTT-", "----G-"]), "DLDDRRRRD")`)
}})

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

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(navigate_trail(["--------", "-CTTT---", "----T---", "---GT---", "--------"]), "RRRDDL")`)
}})

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

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(navigate_trail(["TTTTTTT-", "T-----T-", "T-----T-", "TTTT--TG", "---C----"]), "ULLLUUURRRRRRDDDR")`)
}})

--seed--

--seed-contents--

py
def navigate_trail(map):

    return map

--solutions--

py
def navigate_trail(map):
    rows = len(map)
    cols = len(map[0])

    directions = [
        (0, 1, "R"),
        (1, 0, "D"),
        (0, -1, "L"),
        (-1, 0, "U"),
    ]

    for r in range(rows):
        for c in range(cols):
            if map[r][c] == "C":
                row, col = r, c

    result = ""
    prev = None

    while map[row][col] != "G":
        for dr, dc, move in directions:
            new_row = row + dr
            new_col = col + dc

            if (
                0 <= new_row < rows and
                0 <= new_col < cols and
                (map[new_row][new_col] == "T" or
                 map[new_row][new_col] == "G") and
                (not prev or (new_row, new_col) != prev)
            ):
                result += move
                prev = (row, col)
                row, col = new_row, new_col
                break

    return result