6th assignment

group/assignment6/rearrange_cars.py

@@ -0,0 +1,64 @@
+import unittest
+
+def inverse_map(state):
+    """ Returns array indexed with previous values. """
+    inversed = len(state) * [0]
+
+    for position, car in enumerate(state):
+        inversed[car] = position
+
+    return inversed
+
+def move_car(start, start_position, current_empty):
+    """
+        Moves car from start_position to empty place.
+        Returns new empty place and configuration with moved car.
+    """
+    start[start_position], start[current_empty], current_empty = start[current_empty], start[start_position], start_position
+    return (current_empty, start)
+
+def find_sequence(start, end):
+    """
+        Yields sequence of moves between start and end states.
+    """
+    current_empty = start.index(0)
+    end_positions = inverse_map(end)
+
+    for position in range(len(start)):
+        # At first, move car, that should be placed in current
+        # empty space and repeat.
+        while end_positions[0] != current_empty:
+            start_positions = inverse_map(start)
+            current_empty, start = move_car(start, start_positions[end[current_empty]], current_empty)
+            yield start
+
+        car = start[position]
+
+        if end[position] != car and car != 0:
+            end_position = end_positions[car]
+
+            # Move car from end position to empty place
+            if end_position != current_empty:
+                current_empty, start = move_car(start, end_position, current_empty)
+                yield start
+
+            # Move current car to end position
+            current_empty, start = move_car(start, position, current_empty)
+            yield start
+
+def print_sequence(start, end):
+    print(start)
+    for i in find_sequence(start, end):
+        print(i)
+    print("\n")
+
+class TestCarSequences(unittest.TestCase):
+    def test(self):
+        print_sequence([1, 2, 0, 3], [3, 1, 2, 0])
+        print_sequence([0, 1, 2, 3], [0, 3, 2, 1])
+        print_sequence([1, 2, 3, 4, 0], [2, 1, 0, 4, 3])
+        print_sequence([1, 2, 3, 0], [0, 1, 2, 3])
+        print_sequence([5, 2, 1, 0, 4, 3], [3, 4, 0, 5, 1, 2])
+
+if __name__ == '__main__':
+    unittest.main()