Added "book-store" exercise

config.json

@@ -1245,6 +1245,19 @@
         ],
         "difficulty": 4
       },
+      {
+        "slug": "book-store",
+        "name": "Book Store",
+        "uuid": "dc699152-b327-4493-a485-810a61af69df",
+        "practices": [],
+        "prerequisites": [
+          "loops",
+          "comparisons",
+          "if-statements",
+          "booleans"
+        ],
+        "difficulty": 8
+      },
       {
         "slug": "affine-cipher",
         "name": "Affine Cipher",

exercises/practice/book-store/.docs/instructions.md

@@ -0,0 +1,61 @@
+# Instructions
+
+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 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 (1st, 2nd,3rd, 4th, 5th)
+- 1 group of 3 (1st, 2nd, 3rd)
+
+This would give a total of:
+
+- 5 books at a 25% discount
+- 3 books at a 10% discount
+
+Resulting in:
+
+- 5 × (100% - 25%) × $8 = 5 × $6.00 = $30.00, plus
+- 3 × (100% - 10%) × $8 = 3 × $7.20 = $21.60
+
+Which equals $51.60.
+
+However, a different way to group these 8 books is:
+
+- 1 group of 4 books (1st, 2nd, 3rd, 4th)
+- 1 group of 4 books (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 × (100% - 20%) × $8 = 4 × $6.40 = $25.60, plus
+- 4 × (100% - 20%) × $8 = 4 × $6.40 = $25.60
+
+Which equals $51.20.
+
+And $51.20 is the price with the biggest discount.

exercises/practice/book-store/.meta/config.json

@@ -0,0 +1,21 @@
+{
+  "authors": [
+    "marcelweikum"
+  ],
+  "files": {
+    "solution": [
+      "book_store.cpp",
+      "book_store.h"
+    ],
+    "test": [
+      "book_store_test.cpp"
+    ],
+    "example": [
+      ".meta/example.cpp",
+      ".meta/example.h"
+    ]
+  },
+  "blurb": "To try and encourage more sales of different books from a popular 5 book series, a bookshop has decided to offer discounts of multiple-book purchases.",
+  "source": "Inspired by the harry potter kata from Cyber-Dojo.",
+  "source_url": "https://cyber-dojo.org"
+}

exercises/practice/book-store/.meta/example.cpp

@@ -0,0 +1,66 @@
+#include <array>
+#include <limits>
+#include <map>
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+#include "book_store.h"
+
+namespace book_store {
+
+static const int PRICE_AFTER_DISCOUNT[6] = {0, 800, 1520, 2160, 2560, 3000};
+
+static int dfs(const std::array<int, 5>& state,
+               std::map<std::array<int, 5>, int>& memo) {
+    auto it = memo.find(state);
+    if (it != memo.end()) return it->second;
+
+    bool empty = true;
+    for (int c : state) {
+        if (c > 0) {
+            empty = false;
+            break;
+        }
+    }
+    if (empty) return memo[state] = 0;
+
+    int best = std::numeric_limits<int>::max();
+
+    std::vector<int> idx;
+    for (int i = 0; i < 5; ++i) {
+        if (state[i] > 0) idx.push_back(i);
+    }
+    int n = static_cast<int>(idx.size());
+
+    int maxMask = 1 << n;
+    for (int mask = 1; mask < maxMask; ++mask) {
+        std::array<int, 5> next = state;
+        int k = 0;
+        for (int i = 0; i < n; ++i) {
+            if (mask & (1 << i)) {
+                next[idx[i]]--;
+                ++k;
+            }
+        }
+        int cost = PRICE_AFTER_DISCOUNT[k] + dfs(next, memo);
+        if (cost < best) best = cost;
+    }
+
+    return memo[state] = best;
+}
+
+int total(const std::vector<int>& basket) {
+    std::array<int, 5> counts = {0, 0, 0, 0, 0};
+    for (int id : basket) {
+        if (id < 1 || id > 5) {
+            throw std::invalid_argument("book ID is out of range (1–5)");
+        }
+        counts[id - 1]++;
+    }
+
+    std::map<std::array<int, 5>, int> memo;
+    return dfs(counts, memo);
+}
+
+}  // namespace book_store

exercises/practice/book-store/.meta/example.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <vector>
+
+namespace book_store {
+
+int total(const std::vector<int>& basket);
+
+}  // namespace book_store

exercises/practice/book-store/.meta/tests.toml

@@ -0,0 +1,64 @@
+# 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.
+
+[17146bd5-2e80-4557-ab4c-05632b6b0d01]
+description = "Only a single book"
+
+[cc2de9ac-ff2a-4efd-b7c7-bfe0f43271ce]
+description = "Two of the same book"
+
+[5a86eac0-45d2-46aa-bbf0-266b94393a1a]
+description = "Empty basket"
+
+[158bd19a-3db4-4468-ae85-e0638a688990]
+description = "Two different books"
+
+[f3833f6b-9332-4a1f-ad98-6c3f8e30e163]
+description = "Three different books"
+
+[1951a1db-2fb6-4cd1-a69a-f691b6dd30a2]
+description = "Four different books"
+
+[d70f6682-3019-4c3f-aede-83c6a8c647a3]
+description = "Five different books"
+
+[78cacb57-911a-45f1-be52-2a5bd428c634]
+description = "Two groups of four is cheaper than group of five plus group of three"
+
+[f808b5a4-e01f-4c0d-881f-f7b90d9739da]
+description = "Two groups of four is cheaper than groups of five and three"
+
+[fe96401c-5268-4be2-9d9e-19b76478007c]
+description = "Group of four plus group of two is cheaper than two groups of three"
+
+[68ea9b78-10ad-420e-a766-836a501d3633]
+description = "Two each of first four books and one copy each of rest"
+
+[c0a779d5-a40c-47ae-9828-a340e936b866]
+description = "Two copies of each book"
+
+[18fd86fe-08f1-4b68-969b-392b8af20513]
+description = "Three copies of first book and two each of remaining"
+
+[0b19a24d-e4cf-4ec8-9db2-8899a41af0da]
+description = "Three each of first two books and two each of remaining books"
+
+[bb376344-4fb2-49ab-ab85-e38d8354a58d]
+description = "Four groups of four are cheaper than two groups each of five and three"
+
+[5260ddde-2703-4915-b45a-e54dbbac4303]
+description = "Check that groups of four are created properly even when there are more groups of three than groups of five"
+
+[b0478278-c551-4747-b0fc-7e0be3158b1f]
+description = "One group of one and four is cheaper than one group of two and three"
+
+[cf868453-6484-4ae1-9dfc-f8ee85bbde01]
+description = "One group of one and two plus three groups of four is cheaper than one group of each size"

exercises/practice/book-store/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/book-store/book_store.cpp

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

exercises/practice/book-store/book_store.h

@@ -0,0 +1,10 @@
+#ifndef BOOK_STORE_H
+#define BOOK_STORE_H
+
+namespace book_store {
+
+// TODO: add your solution here
+
+}  // namespace book_store
+
+#endif  // BOOK_STORE_H