Added change exercise

config.json

@@ -1278,6 +1278,19 @@
           "comparisons"
         ],
         "difficulty": 6
+      },
+      {
+        "slug": "change",
+        "name": "Change",
+        "uuid": "e85b5b3e-0ac4-44c4-8b34-fb05b540dc26",
+        "practices": [],
+        "prerequisites": [
+          "exceptions",
+          "lists",
+          "numbers",
+          "loops"
+        ],
+        "difficulty": 5
       }
     ],
     "foregone": [

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

@@ -0,0 +1,8 @@
+# Instructions
+
+Determine the fewest number of coins to give a customer so that the sum of their values equals the correct amount of change.
+
+## Examples
+
+- 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].
+- 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

@@ -0,0 +1,26 @@
+# Introduction
+
+In the mystical village of Coinholt, you stand behind the counter of your bakery, arranging a fresh batch of pastries.
+The door creaks open, and in walks Denara, a skilled merchant with a keen eye for quality goods.
+After a quick meal, she slides a shimmering coin across the counter, representing a value of 100 units.
+
+You smile, taking the coin, and glance at the total cost of the meal: 88 units.
+That means you need to return 12 units in change.
+
+Denara holds out her hand expectantly.
+"Just give me the fewest coins," she says with a smile.
+"My pouch is already full, and I don't want to risk losing them on the road."
+
+You know you have a few options.
+"We have Lumis (worth 10 units), Viras (worth 5 units), and Zenth (worth 2 units) available for change."
+
+You quickly calculate the possibilities in your head:
+
+- one Lumis (1 × 10 units) + one Zenth (1 × 2 units) = 2 coins total
+- two Viras (2 × 5 units) + one Zenth (1 × 2 units) = 3 coins total
+- six Zenth (6 × 2 units) = 6 coins total
+
+"The best choice is two coins: one Lumis and one Zenth," you say, handing her the change.
+
+Denara smiles, clearly impressed.
+"As always, you've got it right."

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

@@ -0,0 +1,21 @@
+{
+  "authors": [
+    "marcelweikum"
+  ],
+  "files": {
+    "solution": [
+      "change.cpp",
+      "change.h"
+    ],
+    "test": [
+      "change_test.cpp"
+    ],
+    "example": [
+      ".meta/example.cpp",
+      ".meta/example.h"
+    ]
+  },
+  "blurb": "Correctly determine change to be given using the least number of coins.",
+  "source": "Software Craftsmanship - Coin Change Kata",
+  "source_url": "https://web.archive.org/web/20130115115225/http://craftsmanship.sv.cmu.edu:80/exercises/coin-change-kata"
+}

exercises/practice/change/.meta/example.cpp

@@ -0,0 +1,46 @@
+#include <algorithm>
+#include <limits>
+#include <stdexcept>
+#include <vector>
+
+#include "change.h"
+
+namespace change {
+
+std::vector<int> find_fewest_coins(const std::vector<int>& coins, int target) {
+    if (target < 0) {
+        throw std::domain_error("target can't be negative");
+    }
+    if (target == 0) {
+        return {};
+    }
+    if (coins.empty()) {
+        throw std::domain_error("can't make target with given coins");
+    }
+
+    std::vector<int> dp(target + 1, std::numeric_limits<int>::max());
+    std::vector<std::vector<int>> solution(target + 1);
+
+    dp[0] = 0;
+
+    for (int i = 1; i <= target; ++i) {
+        for (int coin : coins) {
+            if (i >= coin && dp[i - coin] != std::numeric_limits<int>::max()) {
+                if (dp[i - coin] + 1 < dp[i]) {
+                    dp[i] = dp[i - coin] + 1;
+                    solution[i] = solution[i - coin];
+                    solution[i].push_back(coin);
+                }
+            }
+        }
+    }
+
+    if (dp[target] == std::numeric_limits<int>::max()) {
+        throw std::domain_error("can't make target with given coins");
+    }
+
+    std::sort(solution[target].begin(), solution[target].end());
+    return solution[target];
+}
+
+}  // namespace change

exercises/practice/change/.meta/example.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <vector>
+
+namespace change {
+
+std::vector<int> find_fewest_coins(const std::vector<int>& coins, int target);
+
+}  // namespace change

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

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

exercises/practice/change/CMakeLists.txt

@@ -0,0 +1,67 @@
+# Get the exercise name from the current directory
+get_filename_component(exercise ${CMAKE_CURRENT_SOURCE_DIR} NAME)
+
+# Basic CMake project
+cmake_minimum_required(VERSION 3.5.1)
+
+# Name the project after the exercise
+project(${exercise} CXX)
+
+# Get a source filename from the exercise name by replacing -'s with _'s
+string(REPLACE "-" "_" file ${exercise})
+
+# Implementation could be only a header
+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${file}.cpp)
+    set(exercise_cpp ${file}.cpp)
+else()
+    set(exercise_cpp "")
+endif()
+
+# Use the common Catch library?
+if(EXERCISM_COMMON_CATCH)
+    # For Exercism track development only
+    add_executable(${exercise} ${file}_test.cpp ${exercise_cpp} ${file}.h $<TARGET_OBJECTS:catchlib>)
+elseif(EXERCISM_TEST_SUITE)
+    # The Exercism test suite is being run, the Docker image already
+    # includes a pre-built version of Catch.
+    find_package(Catch2 REQUIRED)
+    add_executable(${exercise} ${file}_test.cpp ${exercise_cpp} ${file}.h)
+    target_link_libraries(${exercise} PRIVATE Catch2::Catch2WithMain)
+    # When Catch is installed system wide we need to include a different
+    # header, we need this define to use the correct one.
+    target_compile_definitions(${exercise} PRIVATE EXERCISM_TEST_SUITE)
+else()
+    # Build executable from sources and headers
+    add_executable(${exercise} ${file}_test.cpp ${exercise_cpp} ${file}.h test/tests-main.cpp)
+endif()
+
+set_target_properties(${exercise} PROPERTIES
+    CXX_STANDARD 17
+    CXX_STANDARD_REQUIRED OFF
+    CXX_EXTENSIONS OFF
+)
+
+set(CMAKE_BUILD_TYPE Debug)
+
+if("${CMAKE_CXX_COMPILER_ID}" MATCHES "(GNU|Clang)")
+    set_target_properties(${exercise} PROPERTIES
+        COMPILE_FLAGS "-Wall -Wextra -Wpedantic -Werror"
+    )
+endif()
+
+# Configure to run all the tests?
+if(${EXERCISM_RUN_ALL_TESTS})
+    target_compile_definitions(${exercise} PRIVATE EXERCISM_RUN_ALL_TESTS)
+endif()
+
+# Tell MSVC not to warn us about unchecked iterators in debug builds
+# Treat warnings as errors
+# Treat type conversion warnings C4244 and C4267 as level 4 warnings, i.e. ignore them in level 3
+if(${MSVC})
+    set_target_properties(${exercise} PROPERTIES
+        COMPILE_DEFINITIONS_DEBUG _SCL_SECURE_NO_WARNINGS
+        COMPILE_FLAGS "/WX /w44244 /w44267")
+endif()
+
+# Run the tests on every build
+add_custom_target(test_${exercise} ALL DEPENDS ${exercise} COMMAND ${exercise})

exercises/practice/change/change.cpp

@@ -0,0 +1,7 @@
+#include "change.h"
+
+namespace change {
+
+// TODO: add your solution here
+
+}  // namespace change

exercises/practice/change/change.h

@@ -0,0 +1,7 @@
+#pragma once
+
+namespace change {
+
+// TODO: add your solution here
+
+}  // namespace change

exercises/practice/change/change_test.cpp

@@ -0,0 +1,83 @@
+#include "change.h"
+#ifdef EXERCISM_TEST_SUITE
+#include <catch2/catch.hpp>
+#else
+#include "test/catch.hpp"
+#endif
+
+TEST_CASE("change_for_1_cent", "[d0ebd0e1-9d27-4609-a654-df5c0ba1d83a]") {
+    REQUIRE(change::find_fewest_coins({1, 5, 10, 25}, 1) ==
+            std::vector<int>{1});
+}
+
+#if defined(EXERCISM_RUN_ALL_TESTS)
+
+TEST_CASE("single_coin_change", "[36887bea-7f92-4a9c-b0cc-c0e886b3ecc8]") {
+    REQUIRE(change::find_fewest_coins({1, 5, 10, 25, 100}, 25) ==
+            std::vector<int>{25});
+}
+
+TEST_CASE("multiple_coin_change", "[cef21ccc-0811-4e6e-af44-f011e7eab6c6]") {
+    REQUIRE(change::find_fewest_coins({1, 5, 10, 25, 100}, 15) ==
+            std::vector<int>{5, 10});
+}
+
+TEST_CASE("change_with_Lilliputian_Coins",
+          "[d60952bc-0c1a-4571-bf0c-41be72690cb3]") {
+    REQUIRE(change::find_fewest_coins({1, 4, 15, 20, 50}, 23) ==
+            std::vector<int>{4, 4, 15});
+}
+
+TEST_CASE("change_with_Lower_Elbonia_Coins",
+          "[408390b9-fafa-4bb9-b608-ffe6036edb6c]") {
+    REQUIRE(change::find_fewest_coins({1, 5, 10, 21, 25}, 63) ==
+            std::vector<int>{21, 21, 21});
+}
+
+TEST_CASE("large_target_values", "[7421a4cb-1c48-4bf9-99c7-7f049689132f]") {
+    REQUIRE(change::find_fewest_coins({1, 2, 5, 10, 20, 50, 100}, 999) ==
+            std::vector<int>{2, 2, 5, 20, 20, 50, 100, 100, 100, 100, 100, 100,
+                             100, 100, 100});
+}
+
+TEST_CASE("possible_change_without_unit_coins",
+          "[f79d2e9b-0ae3-4d6a-bb58-dc978b0dba28]") {
+    REQUIRE(change::find_fewest_coins({2, 5, 10, 20, 50}, 21) ==
+            std::vector<int>{2, 2, 2, 5, 10});
+}
+
+TEST_CASE("another_possible_change_without_unit_coins",
+          "[9a166411-d35d-4f7f-a007-6724ac266178]") {
+    REQUIRE(change::find_fewest_coins({4, 5}, 27) ==
+            std::vector<int>{4, 4, 4, 5, 5, 5});
+}
+
+TEST_CASE("a_greedy_approach_is_not_optimal",
+          "[ce0f80d5-51c3-469d-818c-3e69dbd25f75]") {
+    REQUIRE(change::find_fewest_coins({1, 10, 11}, 20) ==
+            std::vector<int>{10, 10});
+}
+
+TEST_CASE("no_coins_make_0_change", "[bbbcc154-e9e9-4209-a4db-dd6d81ec26bb]") {
+    REQUIRE(change::find_fewest_coins({1, 5, 10, 21, 25}, 0) ==
+            std::vector<int>{});
+}
+
+TEST_CASE("change_smaller_than_smallest_coin",
+          "[c8b81d5a-49bd-4b61-af73-8ee5383a2ce1]") {
+    REQUIRE_THROWS_AS(change::find_fewest_coins({5, 10}, 3), std::domain_error);
+}
+
+TEST_CASE("no_combination_can_make_target",
+          "[3c43e3e4-63f9-46ac-9476-a67516e98f68]") {
+    REQUIRE_THROWS_AS(change::find_fewest_coins({5, 10}, 94),
+                      std::domain_error);
+}
+
+TEST_CASE("cannot_find_negative_change",
+          "[8fe1f076-9b2d-4f44-89fe-8a6ccd63c8f3]") {
+    REQUIRE_THROWS_AS(change::find_fewest_coins({1, 2, 5}, -5),
+                      std::domain_error);
+}
+
+#endif