UPDATED rat_in_maze.py

backtracking/rat_in_maze.py

@@ -1,81 +1,155 @@
 from __future__ import annotations
 
 
-def solve_maze(maze: list[list[int]]) -> bool:
+def solve_maze(
+    maze: list[list[int]],
+    source_row: int,
+    source_column: int,
+    destination_row: int,
+    destination_column: int,
+) -> list[list[int]]:
     """
     This method solves the "rat in maze" problem.
-    In this problem we have some n by n matrix, a start point and an end point.
-    We want to go from the start to the end. In this matrix zeroes represent walls
-    and ones paths we can use.
     Parameters :
-        maze(2D matrix) : maze
+        - maze(2D matrix) : maze
+        - source_row (int): The row index of the starting point.
+        - source_column (int): The column index of the starting point.
+        - destination_row (int): The row index of the destination point.
+        - destination_column (int): The column index of the destination point.
     Returns:
-        Return: True if the maze has a solution or False if it does not.
+        - solution (list[list[int]]): A 2D matrix representing the solution path
+            if it exists.
+    Raises:
+        - ValueError: If no solution exists or if the source or
+            destination coordinates are invalid.
+    Description:
+        This method navigates through a maze represented as an n by n matrix,
+        starting from a specified source cell  and
+        aiming to reach a destination cell.
+        The maze consists of walls (1s) and open paths (0s).
+        By providing custom row and column values, the source and destination
+        cells can be adjusted.
     >>> maze = [[0, 1, 0, 1, 1],
     ...         [0, 0, 0, 0, 0],
     ...         [1, 0, 1, 0, 1],
     ...         [0, 0, 1, 0, 0],
     ...         [1, 0, 0, 1, 0]]
-    >>> solve_maze(maze)
-    [1, 0, 0, 0, 0]
-    [1, 1, 1, 1, 0]
-    [0, 0, 0, 1, 0]
-    [0, 0, 0, 1, 1]
-    [0, 0, 0, 0, 1]
-    True
+    >>> solve_maze(maze,0,0,len(maze)-1,len(maze)-1)    # doctest: +NORMALIZE_WHITESPACE
+    [[0, 1, 1, 1, 1],
+    [0, 0, 0, 0, 1],
+    [1, 1, 1, 0, 1],
+    [1, 1, 1, 0, 0],
+    [1, 1, 1, 1, 0]]
+
+    Note:
+        In the output maze, the zeros (0s) represent one of the possible
+        paths from the source to the destination.
 
     >>> maze = [[0, 1, 0, 1, 1],
     ...         [0, 0, 0, 0, 0],
     ...         [0, 0, 0, 0, 1],
     ...         [0, 0, 0, 0, 0],
     ...         [0, 0, 0, 0, 0]]
-    >>> solve_maze(maze)
-    [1, 0, 0, 0, 0]
-    [1, 0, 0, 0, 0]
-    [1, 0, 0, 0, 0]
-    [1, 0, 0, 0, 0]
-    [1, 1, 1, 1, 1]
-    True
+    >>> solve_maze(maze,0,0,len(maze)-1,len(maze)-1)    # doctest: +NORMALIZE_WHITESPACE
+    [[0, 1, 1, 1, 1],
+    [0, 1, 1, 1, 1],
+    [0, 1, 1, 1, 1],
+    [0, 1, 1, 1, 1],
+    [0, 0, 0, 0, 0]]
 
     >>> maze = [[0, 0, 0],
     ...         [0, 1, 0],
     ...         [1, 0, 0]]
-    >>> solve_maze(maze)
-    [1, 1, 1]
-    [0, 0, 1]
-    [0, 0, 1]
-    True
+    >>> solve_maze(maze,0,0,len(maze)-1,len(maze)-1)    # doctest: +NORMALIZE_WHITESPACE
+    [[0, 0, 0],
+    [1, 1, 0],
+    [1, 1, 0]]
 
-    >>> maze = [[0, 1, 0],
+    >>> maze = [[1, 0, 0],
     ...         [0, 1, 0],
     ...         [1, 0, 0]]
-    >>> solve_maze(maze)
-    No solution exists!
-    False
+    >>> solve_maze(maze,0,1,len(maze)-1,len(maze)-1)    # doctest: +NORMALIZE_WHITESPACE
+    [[1, 0, 0],
+    [1, 1, 0],
+    [1, 1, 0]]
+
+    >>> maze = [[1, 1, 0, 0, 1, 0, 0, 1],
+    ...         [1, 0, 1, 0, 0, 1, 1, 1],
+    ...         [0, 1, 0, 1, 0, 0, 1, 0],
+    ...         [1, 1, 1, 0, 0, 1, 0, 1],
+    ...         [0, 1, 0, 0, 1, 0, 1, 1],
+    ...         [0, 0, 0, 1, 1, 1, 0, 1],
+    ...         [0, 1, 0, 1, 0, 1, 1, 1],
+    ...         [1, 1, 0, 0, 0, 0, 0, 1]]
+    >>> solve_maze(maze,0,2,len(maze)-1,2)  # doctest: +NORMALIZE_WHITESPACE
+    [[1, 1, 0, 0, 1, 1, 1, 1],
+    [1, 1, 1, 0, 0, 1, 1, 1],
+    [1, 1, 1, 1, 0, 1, 1, 1],
+    [1, 1, 1, 0, 0, 1, 1, 1],
+    [1, 1, 0, 0, 1, 1, 1, 1],
+    [1, 1, 0, 1, 1, 1, 1, 1],
+    [1, 1, 0, 1, 1, 1, 1, 1],
+    [1, 1, 0, 1, 1, 1, 1, 1]]
+    >>> maze = [[1, 0, 0],
+    ...         [0, 1, 1],
+    ...         [1, 0, 1]]
+    >>> solve_maze(maze,0,1,len(maze)-1,len(maze)-1)
+    Traceback (most recent call last):
+        ...
+    ValueError: No solution exists!
+
+    >>> maze = [[0, 0],
+    ...         [1, 1]]
+    >>> solve_maze(maze,0,0,len(maze)-1,len(maze)-1)
+    Traceback (most recent call last):
+        ...
+    ValueError: No solution exists!
 
     >>> maze = [[0, 1],
     ...         [1, 0]]
-    >>> solve_maze(maze)
-    No solution exists!
-    False
+    >>> solve_maze(maze,2,0,len(maze)-1,len(maze)-1)
+    Traceback (most recent call last):
+        ...
+    ValueError: Invalid source or destination coordinates
+
+    >>> maze = [[1, 0, 0],
+    ...         [0, 1, 0],
+    ...         [1, 0, 0]]
+    >>> solve_maze(maze,0,1,len(maze),len(maze)-1)
+    Traceback (most recent call last):
+        ...
+    ValueError: Invalid source or destination coordinates
     """
     size = len(maze)
+    # Check if source and destination coordinates are Invalid.
+    if not (0 <= source_row <= size - 1 and 0 <= source_column <= size - 1) or (
+        not (0 <= destination_row <= size - 1 and 0 <= destination_column <= size - 1)
+    ):
+        raise ValueError("Invalid source or destination coordinates")
     # We need to create solution object to save path.
-    solutions = [[0 for _ in range(size)] for _ in range(size)]
-    solved = run_maze(maze, 0, 0, solutions)
+    solutions = [[1 for _ in range(size)] for _ in range(size)]
+    solved = run_maze(
+        maze, source_row, source_column, destination_row, destination_column, solutions
+    )
     if solved:
-        print("\n".join(str(row) for row in solutions))
+        return solutions
     else:
-        print("No solution exists!")
-    return solved
+        raise ValueError("No solution exists!")
 
 
-def run_maze(maze: list[list[int]], i: int, j: int, solutions: list[list[int]]) -> bool:
+def run_maze(
+    maze: list[list[int]],
+    i: int,
+    j: int,
+    destination_row: int,
+    destination_column: int,
+    solutions: list[list[int]],
+) -> bool:
     """
     This method is recursive starting from (i, j) and going in one of four directions:
     up, down, left, right.
     If a path is found to destination it returns True otherwise it returns False.
-    Parameters:
+    Parameters
         maze(2D matrix) : maze
         i, j : coordinates of matrix
         solutions(2D matrix) : solutions
@@ -84,35 +158,41 @@ def run_maze(maze: list[list[int]], i: int, j: int, solutions: list[list[int]])
     """
     size = len(maze)
     # Final check point.
-    if i == j == (size - 1):
-        solutions[i][j] = 1
+    if i == destination_row and j == destination_column and maze[i][j] == 0:
+        solutions[i][j] = 0
         return True
 
     lower_flag = (not i < 0) and (not j < 0)  # Check lower bounds
     upper_flag = (i < size) and (j < size)  # Check upper bounds
 
     if lower_flag and upper_flag:
         # check for already visited and block points.
-        block_flag = (not solutions[i][j]) and (not maze[i][j])
+        block_flag = (solutions[i][j]) and (not maze[i][j])
         if block_flag:
             # check visited
-            solutions[i][j] = 1
+            solutions[i][j] = 0
 
             # check for directions
             if (
-                run_maze(maze, i + 1, j, solutions)
-                or run_maze(maze, i, j + 1, solutions)
-                or run_maze(maze, i - 1, j, solutions)
-                or run_maze(maze, i, j - 1, solutions)
+                run_maze(maze, i + 1, j, destination_row, destination_column, solutions)
+                or run_maze(
+                    maze, i, j + 1, destination_row, destination_column, solutions
+                )
+                or run_maze(
+                    maze, i - 1, j, destination_row, destination_column, solutions
+                )
+                or run_maze(
+                    maze, i, j - 1, destination_row, destination_column, solutions
+                )
             ):
                 return True
 
-            solutions[i][j] = 0
+            solutions[i][j] = 1
             return False
     return False
 
 
 if __name__ == "__main__":
     import doctest
 
-    doctest.testmod()
+    doctest.testmod(optionflags=doctest.NORMALIZE_WHITESPACE)