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Add change exercise
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‎config.json‎

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"prerequisites": [],
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"difficulty": 5
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},
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{
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"slug": "change",
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"name": "Change",
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"uuid": "12729eeb-5129-4c4e-99be-fb9ad623d21a",
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"practices": [],
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"prerequisites": [],
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"difficulty": 6
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},
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{
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"slug": "intergalactic-transmission",
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"name": "Intergalactic Transmission",

‎exercises/practice/change/.docs/instructions.md‎

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# Instructions
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Determine the fewest number of coins to give a customer so that the sum of their values equals the correct amount of change.
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## Examples
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- An amount of 15 with available coin values [1, 5, 10, 25, 100] should return one coin of value 5 and one coin of value 10, or [5, 10].
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- An amount of 40 with available coin values [1, 5, 10, 25, 100] should return one coin of value 5, one coin of value 10, and one coin of value 25, or [5, 10, 25].

‎exercises/practice/change/.docs/introduction.md‎

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# Introduction
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In the mystical village of Coinholt, you stand behind the counter of your bakery, arranging a fresh batch of pastries.
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The door creaks open, and in walks Denara, a skilled merchant with a keen eye for quality goods.
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After a quick meal, she slides a shimmering coin across the counter, representing a value of 100 units.
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You smile, taking the coin, and glance at the total cost of the meal: 88 units.
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That means you need to return 12 units in change.
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Denara holds out her hand expectantly.
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"Just give me the fewest coins," she says with a smile.
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"My pouch is already full, and I don't want to risk losing them on the road."
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You know you have a few options.
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"We have Lumis (worth 10 units), Viras (worth 5 units), and Zenth (worth 2 units) available for change."
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You quickly calculate the possibilities in your head:
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- one Lumis (1 × 10 units) + one Zenth (1 × 2 units) = 2 coins total
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- two Viras (2 × 5 units) + one Zenth (1 × 2 units) = 3 coins total
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- six Zenth (6 × 2 units) = 6 coins total
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"The best choice is two coins: one Lumis and one Zenth," you say, handing her the change.
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Denara smiles, clearly impressed.
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"As always, you've got it right."

‎exercises/practice/change/.meta/config.json‎

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{
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"authors": [
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"keiravillekode"
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],
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"files": {
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"solution": [
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"Change.pas"
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],
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"test": [
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"TestCases.pas"
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],
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"example": [
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".meta/example.pas"
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]
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},
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"blurb": "Correctly determine change to be given using the least number of coins.",
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"source": "Software Craftsmanship - Coin Change Kata",
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"source_url": "https://web.archive.org/web/20130115115225/http://craftsmanship.sv.cmu.edu:80/exercises/coin-change-kata"
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}

‎exercises/practice/change/.meta/example.pas‎

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unit Change;
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{$mode ObjFPC}{$H+}
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interface
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type
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TIntArray = Array Of Integer;
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function findFewestCoins(
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const coins : TIntArray;
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target : Integer
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) : TIntArray;
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implementation
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uses SysUtils;
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function findFewestCoins(
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const coins : TIntArray;
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target : Integer
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) : TIntArray;
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var
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table : TIntArray = ();
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i : Integer;
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j : Integer;
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coin : Integer;
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best : Integer;
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begin
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if target < 0 then
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raise ENotImplemented.Create('target cannot be negative');
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SetLength(table, target + 1);
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table[0] := 0;
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for i := 1 to target do
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begin
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table[i] := target + 1;
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for j := low(coins) to high(coins) do
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begin
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coin := coins[j];
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if (coin <= i) and (table[i] > table[i - coin]) then
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table[i] := table[i - coin] + 1;
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end;
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end;
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if table[target] = target + 1 then
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raise ENotImplemented.Create('cannot make target with given coins');
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result := [];
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while target > 0 do
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begin
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best := -1;
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for j := low(coins) to high(coins) do
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begin
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coin := coins[j];
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if (coin <= target) and ((best = -1) or (table[target - coin] < table[target - best])) then
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best := coin;
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end;
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insert(best, result, length(result));
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target := target - best;
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end;
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end;
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end.

‎exercises/practice/change/.meta/tests.toml‎

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# This is an auto-generated file.
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#
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# Regenerating this file via `configlet sync` will:
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# - Recreate every `description` key/value pair
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# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
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# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
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# - Preserve any other key/value pair
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#
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# As user-added comments (using the # character) will be removed when this file
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# is regenerated, comments can be added via a `comment` key.
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[d0ebd0e1-9d27-4609-a654-df5c0ba1d83a]
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description = "change for 1 cent"
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[36887bea-7f92-4a9c-b0cc-c0e886b3ecc8]
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description = "single coin change"
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[cef21ccc-0811-4e6e-af44-f011e7eab6c6]
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description = "multiple coin change"
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[d60952bc-0c1a-4571-bf0c-41be72690cb3]
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description = "change with Lilliputian Coins"
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[408390b9-fafa-4bb9-b608-ffe6036edb6c]
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description = "change with Lower Elbonia Coins"
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[7421a4cb-1c48-4bf9-99c7-7f049689132f]
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description = "large target values"
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[f79d2e9b-0ae3-4d6a-bb58-dc978b0dba28]
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description = "possible change without unit coins available"
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[9a166411-d35d-4f7f-a007-6724ac266178]
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description = "another possible change without unit coins available"
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[ce0f80d5-51c3-469d-818c-3e69dbd25f75]
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description = "a greedy approach is not optimal"
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[bbbcc154-e9e9-4209-a4db-dd6d81ec26bb]
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description = "no coins make 0 change"
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[c8b81d5a-49bd-4b61-af73-8ee5383a2ce1]
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description = "error testing for change smaller than the smallest of coins"
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[3c43e3e4-63f9-46ac-9476-a67516e98f68]
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description = "error if no combination can add up to target"
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[8fe1f076-9b2d-4f44-89fe-8a6ccd63c8f3]
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description = "cannot find negative change values"

‎exercises/practice/change/Change.pas‎

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unit Change;
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{$mode ObjFPC}{$H+}
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interface
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type
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TIntArray = Array Of Integer;
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function findFewestCoins(
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const coins : TIntArray;
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const target : Integer
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) : TIntArray;
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implementation
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uses SysUtils;
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function findFewestCoins(
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const coins : TIntArray;
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const target : Integer
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) : TIntArray;
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begin
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raise ENotImplemented.Create('Please implement your solution.'); result := [length(coins), target];
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end;
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end.

‎exercises/practice/change/Makefile‎

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SHELL = /bin/bash
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MAKEFLAGS += --no-print-directory
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DESTDIR = build
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EXECUTABLE = $(DESTDIR)/test
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COMMAND = fpc -l- -v0 -g -gl -Sa -Cr -Sehnw -Fu./lib test.pas -FE"./$(DESTDIR)"
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.ONESHELL:
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test:
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@mkdir -p "./$(DESTDIR)"
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@cp -r ./lib "./$(DESTDIR)"
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@$(COMMAND) && ./$(EXECUTABLE) $(test)
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clean:
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@rm -fr "./$(DESTDIR)"

‎exercises/practice/change/TestCases.pas‎

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unit TestCases;
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{$mode ObjFPC}{$H+}
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interface
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uses Classes, SysUtils, FPCUnit, TestRegistry, FPCUnitTestUtils;
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type
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ChangeTest = class(TTestCase)
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published
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procedure change_for_1_cent;
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procedure single_coin_change;
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procedure multiple_coin_change;
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procedure change_with_lilliputian_coins;
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procedure change_with_lower_elbonia_coins;
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procedure large_target_values;
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procedure possible_change_without_unit_coins_available;
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procedure another_possible_change_without_unit_coins_available;
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procedure a_greedy_approach_is_not_optimal;
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procedure no_coins_make_0_change;
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procedure error_testing_for_change_smaller_than_the_smallest_of_coins;
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procedure error_if_no_combination_can_add_up_to_target;
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procedure cannot_find_negative_change_values;
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end;
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implementation
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uses Change;
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procedure TapAssertExpectionMessage(
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ACase : TTestCase ;
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const AMessage : string ;
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const Expected : string ;
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const coins : TIntArray ;
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const target : Integer
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);
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var
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JsonMsg : string;
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actual : string;
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begin
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actual := '';
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try
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findFewestCoins(coins, target);
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except
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on E: Exception do actual := E.Message;
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end;
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JsonMsg := EncodeJsonMessage(AMessage, expected, actual);
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ACase.AssertTrue(JsonMsg, expected = actual);
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end;
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// d0ebd0e1-9d27-4609-a654-df5c0ba1d83a
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procedure ChangeTest.change_for_1_cent;
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begin
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TapAssertTrue(Self, 'change for 1 cent', [1], Change.findFewestCoins([1,5,10,25], 1));
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end;
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// 36887bea-7f92-4a9c-b0cc-c0e886b3ecc8
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procedure ChangeTest.single_coin_change;
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begin
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TapAssertTrue(Self, 'single coin change', [25], Change.findFewestCoins([1,5,10,25,100], 25));
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end;
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// cef21ccc-0811-4e6e-af44-f011e7eab6c6
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procedure ChangeTest.multiple_coin_change;
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begin
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TapAssertTrue(Self, 'multiple coin change', [5,10], Change.findFewestCoins([1,5,10,25,100], 15));
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end;
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// d60952bc-0c1a-4571-bf0c-41be72690cb3
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procedure ChangeTest.change_with_lilliputian_coins;
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begin
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TapAssertTrue(Self, 'change with Lilliputian Coins', [4,4,15], Change.findFewestCoins([1,4,15,20,50], 23));
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end;
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// 408390b9-fafa-4bb9-b608-ffe6036edb6c
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procedure ChangeTest.change_with_lower_elbonia_coins;
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begin
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TapAssertTrue(Self, 'change with Lower Elbonia Coins', [21,21,21], Change.findFewestCoins([1,5,10,21,25], 63));
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end;
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// 7421a4cb-1c48-4bf9-99c7-7f049689132f
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procedure ChangeTest.large_target_values;
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begin
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TapAssertTrue(Self, 'large target values', [2,2,5,20,20,50,100,100,100,100,100,100,100,100,100], Change.findFewestCoins([1,2,5,10,20,50,100], 999));
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end;
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// f79d2e9b-0ae3-4d6a-bb58-dc978b0dba28
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procedure ChangeTest.possible_change_without_unit_coins_available;
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begin
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TapAssertTrue(Self, 'possible change without unit coins available', [2,2,2,5,10], Change.findFewestCoins([2,5,10,20,50], 21));
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end;
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// 9a166411-d35d-4f7f-a007-6724ac266178
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procedure ChangeTest.another_possible_change_without_unit_coins_available;
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begin
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TapAssertTrue(Self, 'another possible change without unit coins available', [4,4,4,5,5,5], Change.findFewestCoins([4,5], 27));
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end;
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// ce0f80d5-51c3-469d-818c-3e69dbd25f75
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procedure ChangeTest.a_greedy_approach_is_not_optimal;
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begin
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TapAssertTrue(Self, 'a greedy approach is not optimal', [10,10], Change.findFewestCoins([1,10,11], 20));
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end;
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// bbbcc154-e9e9-4209-a4db-dd6d81ec26bb
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procedure ChangeTest.no_coins_make_0_change;
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begin
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TapAssertTrue(Self, 'no coins make 0 change', [], Change.findFewestCoins([1,5,10,21,25], 0));
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end;
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// c8b81d5a-49bd-4b61-af73-8ee5383a2ce1
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procedure ChangeTest.error_testing_for_change_smaller_than_the_smallest_of_coins;
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begin
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TapAssertExpectionMessage(Self, 'error testing for change smaller than the smallest of coins', 'cannot make target with given coins', [5,10], 3);
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end;
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// 3c43e3e4-63f9-46ac-9476-a67516e98f68
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procedure ChangeTest.error_if_no_combination_can_add_up_to_target;
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begin
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TapAssertExpectionMessage(Self, 'error if no combination can add up to target', 'cannot make target with given coins', [5,10], 94);
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end;
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// 8fe1f076-9b2d-4f44-89fe-8a6ccd63c8f3
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procedure ChangeTest.cannot_find_negative_change_values;
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begin
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TapAssertExpectionMessage(Self, 'cannot find negative change values', 'target cannot be negative', [1,2,5], -5);
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end;
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initialization
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RegisterTest(ChangeTest);
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end.

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