Can You Reach the Exit?

Challenge Difficulty: Medium | Estimated completion time: ~25 minutes

You are given a 2D grid where each cell is one of:

• '.' - empty space (you can walk here)
• '#' - wall (you cannot walk here)
• '@' - starting position
• 'E' - exit

You can move up, down, left, right (no diagonals), and you cannot move outside the grid.

Examples

can_reach_exit([
    "@..",
    ".#E",
    "..."
])
output = True
# One path: (0,0)->(0,1)->(0,2)->(1,2) which is 'E'
 
can_reach_exit([
    "@#E"
])
output = False
# Exit is blocked by a wall
 
can_reach_exit([
    "@.#.",
    "..#E",
    "####"
])
output = False
 
can_reach_exit([
    "@...",
    ".###",
    "...E"
])
output = True

Solution

Python

from collections import deque def can_reach_exit(grid: list[str]) -> bool: """Check if you can reach the exit from the starting position. Args: grid: 2D grid where '@' is start, 'E' is exit, '#' is wall, '.' is empty Returns: True if exit is reachable, False otherwise """ rows = len(grid) columns = len(grid[0]) if rows > 0 else 0 start_row, start_column = 0, 0 for row_index in range(rows): for column_index in range(columns): if grid[row_index][column_index] == "@": start_row, start_column = row_index, column_index break queue = deque([(start_row, start_column)]) visited = {(start_row, start_column)} directions = [(0, 1), (1, 0), (0, -1), (-1, 0)] while queue: current_row, current_column = queue.popleft() if grid[current_row][current_column] == "E": return True for delta_row, delta_column in directions: new_row = current_row + delta_row new_column = current_column + delta_column if (0 <= new_row < rows and 0 <= new_column < columns and (new_row, new_column) not in visited and grid[new_row][new_column] != "#"): visited.add((new_row, new_column)) queue.append((new_row, new_column)) return False if __name__ == "__main__": print(can_reach_exit(["@..", ".#E", "..."])) # True print(can_reach_exit(["@#E"])) # False print(can_reach_exit(["@.#.", "..#E", "####"])) # False print(can_reach_exit(["@...", ".###", "...E"])) # True

Output