Software Engineering

Help the Bookseller Challenge in Python


A bookseller has lots of books classified in 26 categories labeled A, B, … Z. Each book has a code c of 3, 4, 5 or more characters. The 1st character of a code is a capital letter which defines the book category.

In the bookseller’s stocklist each code c is followed by a space and by a positive integer n (int n >= 0) which indicates the quantity of books of this code in stock.

For example an extract of a stocklist could be:

L = {"ABART 20", "CDXEF 50", "BKWRK 25", "BTSQZ 89", "DRTYM 60"}.
or
L = ["ABART 20", "CDXEF 50", "BKWRK 25", "BTSQZ 89", "DRTYM 60"] or ....
You will be given a stocklist (e.g. : L) and a list of categories in capital letters e.g :

M = {"A", "B", "C", "W"}
or
M = ["A", "B", "C", "W"] or ...
and your task is to find all the books of L with codes belonging to each category of M and to sum their quantity according to each category.

For the lists L and M of example you have to return the string:

(A : 20) - (B : 114) - (C : 50) - (W : 0)
where A, B, C, W are the categories, 20 is the sum of the unique book of category A, 114 the sum corresponding to “BKWRK” and “BTSQZ”, 50 corresponding to “CDXEF” and 0 to category ‘W’ since there are no code beginning with W.

If L or M are empty return string is “”.

Notes:

  • In the result codes and their values are in the same order as in M.
  • See “Samples Tests” for the return.

The Solution in Python

Option 1

def stock_list(listOfArt, listOfCat):
    if (len(listOfArt) == 0) or (len(listOfCat) == 0):
        return ""
    result = ""
    for cat in listOfCat:
        total = 0
        for book in listOfArt:
            if (book[0] == cat[0]):
                total += int(book.split(" ")[1])
        if (len(result) != 0):
            result += " - "
        result += "(" + str(cat) + " : " + str(total) + ")"
    return result

Option 2

from collections import Counter

def stock_list(listOfArt, listOfCat):
    if not listOfArt:
        return ''
    codePos = listOfArt[0].index(' ') + 1
    cnt = Counter()
    for s in listOfArt:
        cnt[s[0]] += int(s[codePos:])
    return ' - '.join('({} : {})'.format(cat, cnt[cat]) for cat in listOfCat)

Option 3

def stock_list(stocklist, categories):
    if not stocklist or not categories:
        return ""
    return " - ".join(
        "({} : {})".format(
            category,
            sum(int(item.split()[1]) for item in stocklist if item[0] == category))
        for category in categories)

Test cases to validate the solution

from solution import stock_list
import test

@test.describe("Testing")
def _():
    @test.it("Tests")
    def _():
        b = ["BBAR 150", "CDXE 515", "BKWR 250", "BTSQ 890", "DRTY 600"]
        c = ["A", "B", "C", "D"]
        test.assert_equals(stock_list(b, c), "(A : 0) - (B : 1290) - (C : 515) - (D : 600)")

        b = ["ABAR 200", "CDXE 500", "BKWR 250", "BTSQ 890", "DRTY 600"]
        c = ["A", "B"]
        test.assert_equals(stock_list(b, c), "(A : 200) - (B : 1140)")

        b = ["CBART 20", "CDXEF 50", "BKWRK 25", "BTSQZ 89", "DRTYM 60"]
        c = ["A", "B", "C", "W"]
        test.assert_equals(stock_list(b, c), "(A : 0) - (B : 114) - (C : 70) - (W : 0)")

        b = ["ROXANNE 102", "RHODODE 123", "BKWRKAA 125", "BTSQZFG 239", "DRTYMKH 060"]
        c = ["B", "R", "D", "X"]
        test.assert_equals(stock_list(b, c), "(B : 364) - (R : 225) - (D : 60) - (X : 0)")

        b = []
        c = ["B", "R", "D", "X"]
        test.assert_equals(stock_list(b, c), "")

        b = ["ROXANNE 102", "RHODODE 123", "BKWRKAA 125", "BTSQZFG 239", "DRTYMKH 060"]
        c = []
        test.assert_equals(stock_list(b, c), "")

        b = ["ROXANNE 102", "RHODODE 123", "BKWRKAA 125", "BTSQZFG 239", "DRTYMKH 060"]
        c = ["U", "V", "R"]
        test.assert_equals(stock_list(b, c), "(U : 0) - (V : 0) - (R : 225)")