Add knapsack (#945)

* Add knapsack

* Extract local variables for items and item_count even when there are no items

* Use updated UNITY_BEGIN/END macro calls

config.json

@@ -1048,6 +1048,14 @@
           "control_flow_if_statements",
           "control_flow_loops"
         ]
+      },
+      {
+        "slug": "knapsack",
+        "name": "Knapsack",
+        "uuid": "caf3784a-400f-425d-b537-a903175503ff",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 7
       }
     ]
   },

exercises/practice/knapsack/.docs/instructions.md

@@ -0,0 +1,35 @@
+# Instructions
+
+In this exercise, let's try to solve a classic problem.
+
+Bob is a thief.
+After months of careful planning, he finally manages to crack the security systems of a high-class apartment.
+
+In front of him are many items, each with a value (v) and weight (w).
+Bob, of course, wants to maximize the total value he can get; he would gladly take all of the items if he could.
+However, to his horror, he realizes that the knapsack he carries with him can only hold so much weight (W).
+
+Given a knapsack with a specific carrying capacity (W), help Bob determine the maximum value he can get from the items in the house.
+Note that Bob can take only one of each item.
+
+All values given will be strictly positive.
+Items will be represented as a list of items.
+Each item will have a weight and value.
+
+For example:
+
+```none
+Items: [
+  { "weight": 5, "value": 10 },
+  { "weight": 4, "value": 40 },
+  { "weight": 6, "value": 30 },
+  { "weight": 4, "value": 50 }
+]
+
+Knapsack Limit: 10
+```
+
+For the above, the first item has weight 5 and value 10, the second item has weight 4 and value 40, and so on.
+
+In this example, Bob should take the second and fourth item to maximize his value, which, in this case, is 90.
+He cannot get more than 90 as his knapsack has a weight limit of 10.

exercises/practice/knapsack/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": ["ryanplusplus"],
+  "files": {
+    "solution": [
+      "knapsack.c",
+      "knapsack.h"
+    ],
+    "test": [
+      "test_knapsack.c"
+    ],
+    "example": [
+      ".meta/example.c",
+      ".meta/example.h"
+    ]
+  },
+  "blurb": "Given a knapsack that can only carry a certain weight, determine which items to put in the knapsack in order to maximize their combined value.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Knapsack_problem"
+}

exercises/practice/knapsack/.meta/example.c

@@ -0,0 +1,28 @@
+#include <string.h>
+#include "knapsack.h"
+
+unsigned int maximum_value(unsigned int maximum_weight, item_t *items,
+                           size_t item_count)
+{
+   unsigned int table[item_count + 1][maximum_weight + 1];
+   memset(table, 0, sizeof(table));
+
+   for (size_t i = 0; i < item_count; i++) {
+      for (unsigned int capacity = 1; capacity <= maximum_weight; capacity++) {
+         unsigned int weight = items[i].weight;
+         unsigned int value = items[i].value;
+
+         if (weight > capacity) {
+            table[i + 1][capacity] = table[i][capacity];
+         } else if (table[i][capacity] <= value + table[i][capacity - weight]) {
+            table[i + 1][capacity] = value + table[i][capacity - weight];
+         } else {
+            table[i + 1][capacity] = table[i][capacity];
+         }
+      }
+   }
+
+   unsigned int result = table[item_count][maximum_weight];
+
+   return result;
+}

exercises/practice/knapsack/.meta/example.h

@@ -0,0 +1,14 @@
+#ifndef KNAPSACK_H
+#define KNAPSACK_H
+
+#include <stddef.h>
+
+typedef struct {
+   unsigned int weight;
+   unsigned int value;
+} item_t;
+
+unsigned int maximum_value(unsigned int maximum_weight, item_t *items,
+                           size_t item_count);
+
+#endif

exercises/practice/knapsack/.meta/tests.toml

@@ -0,0 +1,36 @@
+# 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.
+
+[a4d7d2f0-ad8a-460c-86f3-88ba709d41a7]
+description = "no items"
+include = false
+
+[3993a824-c20e-493d-b3c9-ee8a7753ee59]
+description = "no items"
+reimplements = "a4d7d2f0-ad8a-460c-86f3-88ba709d41a7"
+
+[1d39e98c-6249-4a8b-912f-87cb12e506b0]
+description = "one item, too heavy"
+
+[833ea310-6323-44f2-9d27-a278740ffbd8]
+description = "five items (cannot be greedy by weight)"
+
+[277cdc52-f835-4c7d-872b-bff17bab2456]
+description = "five items (cannot be greedy by value)"
+
+[81d8e679-442b-4f7a-8a59-7278083916c9]
+description = "example knapsack"
+
+[f23a2449-d67c-4c26-bf3e-cde020f27ecc]
+description = "8 items"
+
+[7c682ae9-c385-4241-a197-d2fa02c81a11]
+description = "15 items"

exercises/practice/knapsack/knapsack.c

@@ -0,0 +1 @@
+#include "knapsack.h"

exercises/practice/knapsack/knapsack.h

@@ -0,0 +1,9 @@
+#ifndef KNAPSACK_H
+#define KNAPSACK_H
+
+typedef struct {
+   unsigned int weight;
+   unsigned int value;
+} item_t;
+
+#endif

exercises/practice/knapsack/makefile

@@ -0,0 +1,37 @@
+### If you wish to use extra libraries (math.h for instance),
+### add their flags here (-lm in our case) in the "LIBS" variable.
+
+LIBS = -lm
+
+###
+CFLAGS  = -std=c99
+CFLAGS += -g
+CFLAGS += -Wall
+CFLAGS += -Wextra
+CFLAGS += -pedantic
+CFLAGS += -Werror
+CFLAGS += -Wmissing-declarations
+CFLAGS += -DUNITY_SUPPORT_64 -DUNITY_OUTPUT_COLOR
+
+ASANFLAGS  = -fsanitize=address
+ASANFLAGS += -fno-common
+ASANFLAGS += -fno-omit-frame-pointer
+
+.PHONY: test
+test: tests.out
+	@./tests.out
+
+.PHONY: memcheck
+memcheck: ./*.c ./*.h
+	@echo Compiling $@
+	@$(CC) $(ASANFLAGS) $(CFLAGS) test-framework/unity.c ./*.c -o memcheck.out $(LIBS)
+	@./memcheck.out
+	@echo "Memory check passed"
+
+.PHONY: clean
+clean:
+	rm -rf *.o *.out *.out.dSYM
+
+tests.out: ./*.c ./*.h
+	@echo Compiling $@
+	@$(CC) $(CFLAGS) test-framework/unity.c ./*.c -o tests.out $(LIBS)