intro2ai/p0_tutorial/shopAroundTown.py

# shopAroundTown.py
# -----------------
# Licensing Information:  You are free to use or extend these projects for
# educational purposes provided that (1) you do not distribute or publish
# solutions, (2) you retain this notice, and (3) you provide clear
# attribution to UC Berkeley, including a link to http://ai.berkeley.edu.
# 
# Attribution Information: The Pacman AI projects were developed at UC Berkeley.
# The core projects and autograders were primarily created by John DeNero
# (denero@cs.berkeley.edu) and Dan Klein (klein@cs.berkeley.edu).
# Student side autograding was added by Brad Miller, Nick Hay, and
# Pieter Abbeel (pabbeel@cs.berkeley.edu).


"""
Here's the intended output of this script, once you fill it in:

Welcome to shop1 fruit shop
Welcome to shop2 fruit shop
Welcome to shop3 fruit shop
Orders: [('apples', 1.0), ('oranges', 3.0), ('limes', 2.0)]
At gas price 1 the best route is: ['shop1', 'shop2', 'shop3']
At gas price 3 the best route is: ['shop1', 'shop3']
At gas price 5 the best route is: ['shop2']
At gas price -1 the best route is: ['shop2', 'shop1', 'shop3']
"""

import shop
import town

def shopAroundTown(orderList, fruitTown, gasCost):
    """
        orderList: List of (fruit, numPound) tuples
        fruitTown: A Town object
        gasCost: A number representing the cost of going one mile
    Returns a list of shops in the order that is the optimal route to take when
    buying the fruit in the orderList
    """
    possibleRoutes = []
    subsets = getAllSubsets(fruitTown.getShops())
    for subset in subsets:
        names = [ shop.getName() for shop in subset ]
        if fruitTown.allFruitsCarriedAtShops(orderList, names):
            possibleRoutes += getAllPermutations(subset)
    minCost, bestRoute = None, None
    for route in possibleRoutes:
        cost = fruitTown.getPriceOfOrderOnRoute(orderList, route, gasCost)
        if minCost == None or cost < minCost:
            minCost, bestRoute = cost, route
    return bestRoute

def getAllSubsets(lst):
    """
        lst: A list
    Returns the powerset of lst, i.e. a list of all the possible subsets of lst
    """
    if not lst:
        return []
    withFirst = [ [lst[0]] + rest for rest in getAllSubsets(lst[1:]) ]
    withoutFirst = getAllSubsets(lst[1:])
    return withFirst + withoutFirst

def getAllPermutations(lst):
    """
        lst: A list
    Returns a list of all permutations of lst
    """
    if not lst: 
        return []
    elif len(lst) == 1:
        return lst
    allPermutations = []
    for i in range(len(lst)):
        item = lst[i]
        withoutItem = lst[:i] + lst[i:]
        allPermutations += prependToAll(item, getAllPermutations(withoutItem))
    return allPermutations

def prependToAll(item, lsts):
    """
        item: Any object
        lsts: A list of lists
    Returns a copy of lsts with item prepended to each list contained in lsts
    """
    return [ [item] + lst for lst in lsts ]

if __name__ == '__main__':
    "This code runs when you invoke the script from the command line"
    orders = [('apples', 1.0), ('oranges', 3.0), ('limes', 2.0)]
    dir1 = {'apples': 2.0, 'oranges': 1.0}
    dir2 = {'apples': 1.0, 'oranges': 5.0, 'limes': 3.0}
    dir3 = {'apples': 2.0, 'limes': 2.0}
    shop1 = shop.FruitShop('shop1', dir1)
    shop2 = shop.FruitShop('shop2', dir2)
    shop3 = shop.FruitShop('shop3', dir3)
    shops = [shop1, shop2, shop3]
    distances = { ('home', 'shop1') : 2,
                  ('home', 'shop2') : 1,
                  ('home', 'shop3') : 1,
                  ('shop1', 'shop2') : 2.5,
                  ('shop1', 'shop3') : 2.5,
                  ('shop2', 'shop3') : 1 
                }
    fruitTown = town.Town(shops, distances)
    print "Orders:", orders
    for price in (1, 3, 5, -1):
        print "At gas price", price, "the best route is:", \
                shopAroundTown(orders, fruitTown, price)