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rpottsoh's solution

to Book Store in the Delphi Pascal Track

Published at Sep 17 2018 · 0 comments
Instructions
Test suite
Solution

Note:

This exercise has changed since this solution was written.

To try and encourage more sales of different books from a popular 5 book series, a bookshop has decided to offer discounts on multiple book purchases.

One copy of any of the five books costs \$8.

If, however, you buy two different books, you get a 5% discount on those two books.

If you buy 3 different books, you get a 10% discount.

If you buy 4 different books, you get a 20% discount.

If you buy all 5, you get a 25% discount.

Note: that if you buy four books, of which 3 are different titles, you get a 10% discount on the 3 that form part of a set, but the fourth book still costs \$8.

Your mission is to write a piece of code to calculate the price of any conceivable shopping basket (containing only books of the same series), giving as big a discount as possible.

For example, how much does this basket of books cost?

• 2 copies of the first book
• 2 copies of the second book
• 2 copies of the third book
• 1 copy of the fourth book
• 1 copy of the fifth book

One way of grouping these 8 books is:

• 1 group of 5 --> 25% discount (1st,2nd,3rd,4th,5th)
• +1 group of 3 --> 10% discount (1st,2nd,3rd)

This would give a total of:

• 5 books at a 25% discount
• +3 books at a 10% discount

Resulting in:

• 5 x (8 - 2.00) == 5 x 6.00 == \$30.00
• +3 x (8 - 0.80) == 3 x 7.20 == \$21.60

For a total of \$51.60

However, a different way to group these 8 books is:

• 1 group of 4 books --> 20% discount (1st,2nd,3rd,4th)
• +1 group of 4 books --> 20% discount (1st,2nd,3rd,5th)

This would give a total of:

• 4 books at a 20% discount
• +4 books at a 20% discount

Resulting in:

• 4 x (8 - 1.60) == 4 x 6.40 == \$25.60
• +4 x (8 - 1.60) == 4 x 6.40 == \$25.60

For a total of \$51.20

And \$51.20 is the price with the biggest discount.

Testing

In order to run the tests for this track, you will need to install DUnitX. Please see the installation instructions for more information.

If Delphi is properly installed, and `*.dpr` file types have been associated with Delphi, then double clicking the supplied `*.dpr` file will start Delphi and load the exercise/project. `control + F9` is the keyboard shortcut to compile the project or pressing `F9` will compile and run the project.

Alternatively you may opt to start Delphi and load your project via. the `File` drop down menu.

When Questions Come Up

We monitor the Pascal-Delphi support room on gitter.im to help you with any questions that might arise.

Submitting Exercises

Note that, when trying to submit an exercise, make sure the exercise file you're submitting is in the `exercism/delphi/<exerciseName>` directory.

For example, if you're submitting `ubob.pas` for the Bob exercise, the submit command would be something like `exercism submit <path_to_exercism_dir>/delphi/bob/ubob.pas`.

Source

Inspired by the harry potter kata from Cyber-Dojo. http://cyber-dojo.org

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

uBookStoreTests.pas

``````unit uBookStoreTests;

interface
uses
DUnitX.TestFramework;

const
CanonicalVersion = '1.3.0';

type
[TestFixture]
hpTests = class(TObject)
public
[Test]
//    [Ignore('Comment the "[Ignore]" statement to run the test')]

[Test]
[Ignore]

[Test]
[Ignore]

[Test]
[Ignore]

[Test]
[Ignore]

[Test]
[Ignore]

[Test]
[Ignore]

[Test]
[Ignore]

[Test]
[Ignore]

[Test]
[Ignore]

[Test]
[Ignore]

[Test]
[Ignore]

[Test]
[Ignore]
procedure Four_groups_of_four_are_cheaper_than_two_groups_each_of_five_and_three;
end;

implementation
uses System.SysUtils, uBookStore;

Expected: integer;
begin
Expected := 800;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 1600;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 0;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 1520;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 2160;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

procedure hpTests.Four_groups_of_four_are_cheaper_than_two_groups_each_of_five_and_three;
Expected: integer;
begin
Expected := 10240;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 2560;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 3000;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 5120;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 5560;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 6000;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 6800;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

Expected: integer;
begin
Expected := 7520;

assert.AreEqual(Expected, fBasket.Total, format('Total should be %d cents',[Expected]));
end;

initialization
TDUnitX.RegisterTestFixture(hpTests);
end.``````
``````unit uBookStore;

interface

type
['{22B4BAF3-88E6-456D-9DE5-F6BAC743A655}']
function Total:extended;
end;

implementation
uses System.SysUtils, System.Generics.collections, System.Math;

const
seriesBooks = '12345';
cNumberOfBooks = 5;
cDiscounts: array[1..cNumberOfBooks] of extended = (1.00,
0.95,
0.90,
0.80,
0.75);

type
private
fSingleBookPrice: extended;
fIntList: TList<integer>;
class function Head(inStr: string): string; static;
class function Tail(inStr: string): string; static;
class function ConvertIntArrayToString(const aIntArray: TArray<Integer>): string; static;
function DiscountPercentage(inStr : string): extended;
function NumberOfDifferentBooks(inStr : string):integer;
public
function Total:extended;
end;

begin
end;

begin
result := inStr.Remove(1);
end;

class function TBasket.Tail(inStr : string):string;
begin
result := inStr.Remove(0,1);
end;

class function TBasket.ConvertIntArrayToString(const aIntArray: TArray<Integer>): string;
var arrayItem: integer;
begin
result := '';
if length(aIntArray) > 0 then
for arrayItem in aIntArray do
result := result + arrayItem.ToString;
end;

begin
fSingleBookPrice := 8;
fIntList := TList<integer>.Create;
fIntList.Sort;
end;

var lStrArray: TArray<String>;
tmpStr   : string;
thisBook : string;
Index    : integer;
StrCount : integer;
begin
StrCount := 1;
SetLength(lStrArray,StrCount);
while wrkBasket.Length > 0 do
begin
Index := 0;
repeat
tmpStr := lStrArray[Index];
if thisBook.Length > 0 then
begin
if not tmpStr.Contains(thisBook) then
begin
tmpStr := tmpStr + thisBook;
lStrArray[Index] := tmpStr;
end
else
if (Index = StrCount - 1) then
begin
inc(StrCount);
SetLength(lStrArray,StrCount);
end;
inc(Index);
end;
until (Index = StrCount) or wrkBasket.IsEmpty;
end;
result := lStrArray;
end;

var
subResult     : array[0..1] of extended;

function computeTotal: extended;
totalBooks  : integer;
subTotal    : extended;
begin
result := 0;
begin
subTotal := totalBooks * (fSingleBookPrice * DiscountPercentage(wrkSubBasket));
Result := Result + subTotal;
end;
end;

begin
fillchar(subResult, sizeof(extended), #0);

subResult[0] := computeTotal;

subResult[1] := computeTotal;

result := min(subResult[0], subResult[1]);
end;

function TBasket.DiscountPercentage(inStr : string):extended;
var numDiffBooks: integer;
begin
numDiffBooks := NumberOfDifferentBooks(inStr);
result := CDiscounts[numDiffBooks];
end;

function TBasket.NumberOfDifferentBooks(inStr : string):integer;
var Book: char;
begin
result := 0;
for Book in seriesBooks do
if inStr.Contains(Book) then
inc(result);
end;

end.``````