Added data integrity validation function.

This is to make sure that the distances.txt file does not contain any
mismatched data (as it currently does).
The user will be propmpted for input for each city that contains
false data.

data_validation.py

@@ -13,4 +13,20 @@ def generate_matrix(default=None):
                 path_len = [i for i in val[0].split("\t")]
                 matrix.append([int(i) for i in path_len[1:]])
 
+        cities.pop(0)
+        for i in range(0, len(matrix)):
+            for j in range(0, len(matrix[i])):
+                if matrix[i][j] != matrix[j][i]:
+                    if default is None:
+                        print(
+                            f"Mismatched distances between {cities[i]}",
+                            f"and {cities[j]}.",
+                            f"\nCurrent values are: {matrix[i][j]} {matrix[j][i]}.",
+                            "To continue, enter a new value:"
+                        )
+                        new_distance = input()
+                    else:
+                        new_distance = default
+                    matrix[i][j] = new_distance
+                    matrix[j][i] = new_distance
     return {"matrix": matrix, "cities": cities}
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