Update travelling_salesman_problem.py

Author: OmMahajan29

dynamic_programming/travelling_salesman_problem.py

@@ -1,18 +1,15 @@
 #!/usr/bin/env python3
 
-
 def tsp(distances: list[list[int]]) -> int:
     """
     Solves the Travelling Salesman Problem (TSP)
     using dynamic programming and bitmasking.
-
     Args:
         distances: 2D list where distances[i][j]
         is the distance between city i and city j.
-
     Returns:
-        Minimum cost to complete the tour visiting all cities.
-
+        Minimum cost to complete the 
+        tour visiting all cities.
     Raises:
         ValueError: If any distance is negative.
 
@@ -31,18 +28,17 @@ def tsp(distances: list[list[int]]) -> int:
     n = len(distances)
     if any(distances[i][j] < 0 for i in range(n) for j in range(n)):
         raise ValueError("Distance cannot be negative")
-
     # Memoization table
     memo = [[-1] * (1 << n) for _ in range(n)]
     visited_all = (1 << n) - 1  # All cities visited mask
-
     def visit(city: int, mask: int) -> int:
         """Recursively calculates the minimum cost to visit all cities."""
         if mask == visited_all:
             return distances[city][0]  # Return to the starting city
+
         if memo[city][mask] != -1:  # Return cached result if exists
             return memo[city][mask]
-        min_cost = float("inf")  # Use infinity for initial comparison
+        min_cost = float('inf')  # Use infinity for initial comparison
         for next_city in range(n):
             if not (mask & (1 << next_city)):  # If unvisited
                 new_cost = distances[city][next_city] + visit(
@@ -51,11 +47,10 @@ def visit(city: int, mask: int) -> int:
                 min_cost = min(min_cost, new_cost)
         memo[city][mask] = int(min_cost)  # Store result as an integer
         return memo[city][mask]  # Return the cached result
-
     return visit(0, 1)  # Start from city 0 with city 0 visited
-
-
 if __name__ == "__main__":
     import doctest
-
-    doctest.testmod()
+    try:
+        doctest.testmod()
+    except Exception as e:
+        print(f"An error occurred during doctest: {e}")