cost_prorating.py

import math

def cost_prorating(cost:float, weights:list[float]):

    if cost < 0:
        raise ValueError("Cost must be non-negative.")
    if not weights:
        raise ValueError("Weights list cannot be empty.")
    if not all(w >= 0 for w in weights):
        raise ValueError("All weights must be non-negative.")
    total = sum(weights)
    


    if total == 0:
         if cost == 0:
             return [0] * len(weights)
         else:
             raise ValueError("Total weight is zero, cannot distribute positive cost.")
    
    prorated_cost = [0] * len(weights)
    remainders = [0] * len(weights)
    current_allocation_total = 0
    for i in range(len(weights)):
        if weights[i] == 0:
            prorated_cost[i] = 0
        elif weights[i] > 0:  
            exact_share = (cost * weights[i]) / total
            prorated_cost[i] = math.floor(exact_share)
            remainders[i] = exact_share - prorated_cost[i]
    unassigned_cost = cost - sum(prorated_cost)

    return prorated_cost


## Set your own values for cost and weights or comment for the examples below
try:
    cost = float(input("Enter the total cost to prorate: "))
    
    weights = []
    print("Enter weights (enter 'done' when finished)")
    while True:
        weight_input = input("Enter a weight (or 'done' to finish): ")
        if weight_input.lower() == 'done':
            break
        weights.append(float(weight_input))
    
    result = cost_prorating(cost, weights)
    print(f"Prorated costs: {result}")
except ValueError as e:
    print(f"Error: {e}")






# cost1 = 100
# weights1 = [10, 20, 70]
# print(f"Cost: {cost1}, Weights: {weights1}, Prorated: {prorate_cost(cost1, weights1)}")
# # Expected: [10, 20, 70] (Exact shares are integers)

# cost2 = 100
# weights2 = [1, 1, 1]
# print(f"Cost: {cost2}, Weights: {weights2}, Prorated: {prorate_cost(cost2, weights2)}")
# # Expected: [34, 33, 33] or similar. Exact = 33.33... Remainders all 0.33...
# # Floor = [33, 33, 33]. Sum = 99. Remainder units = 1.
# # Give 1 unit to one with largest remainder (they are equal, first one gets it). Output: [34, 33, 33]

# cost3 = 7
# weights3 = [1, 2, 3, 0]
# print(f"Cost: {cost3}, Weights: {weights3}, Prorated: {prorate_cost(cost3, weights3)}")
# # Total weight = 6.
# # Exact: [1.166, 2.333, 3.5, 0]
# # Floor: [1, 2, 3, 0]. Sum = 6. Remainder units = 1.
# # Fractions: [0.166, 0.333, 0.5, -1]. Sorted indices by fraction: 2, 1, 0, 3
# # Give 1 unit to index 2.
# # Expected: [1, 2, 4, 0]