add exercise zebra-puzzle (#959)

* add exercise zebra-puzzle

* Update exercises/practice/zebra-puzzle/zebra_puzzle.h

* Update config.json

* Format

---------

Co-authored-by: Ryan Hartlage <ryanplusplus@gmail.com>

config.json

@@ -1049,6 +1049,14 @@
           "control_flow_loops"
         ]
       },
+      {
+        "slug": "zebra-puzzle",
+        "name": "Zebra Puzzle",
+        "uuid": "2cae2796-5c05-4159-b3e7-9f5653f0bc9b",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 6
+      },
       {
         "slug": "knapsack",
         "name": "Knapsack",

exercises/practice/zebra-puzzle/.docs/instructions.md

@@ -0,0 +1,24 @@
+# Instructions
+
+Solve the zebra puzzle.
+
+1. There are five houses.
+2. The Englishman lives in the red house.
+3. The Spaniard owns the dog.
+4. Coffee is drunk in the green house.
+5. The Ukrainian drinks tea.
+6. The green house is immediately to the right of the ivory house.
+7. The Old Gold smoker owns snails.
+8. Kools are smoked in the yellow house.
+9. Milk is drunk in the middle house.
+10. The Norwegian lives in the first house.
+11. The man who smokes Chesterfields lives in the house next to the man with the fox.
+12. Kools are smoked in the house next to the house where the horse is kept.
+13. The Lucky Strike smoker drinks orange juice.
+14. The Japanese smokes Parliaments.
+15. The Norwegian lives next to the blue house.
+
+Each of the five houses is painted a different color, and their inhabitants are of different national extractions, own different pets, drink different beverages and smoke different brands of cigarettes.
+
+Which of the residents drinks water?
+Who owns the zebra?

exercises/practice/zebra-puzzle/.meta/config.json

@@ -0,0 +1,21 @@
+{
+  "authors": [
+    "siebenschlaefer"
+  ],
+  "files": {
+    "solution": [
+      "zebra_puzzle.c",
+      "zebra_puzzle.h"
+    ],
+    "test": [
+      "test_zebra_puzzle.c"
+    ],
+    "example": [
+      ".meta/example.c",
+      ".meta/example.h"
+    ]
+  },
+  "blurb": "Solve the zebra puzzle.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Zebra_Puzzle"
+}

exercises/practice/zebra-puzzle/.meta/example.c

@@ -0,0 +1,203 @@
+#include "zebra_puzzle.h"
+#include <assert.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+enum { NUM_HOUSES = 5 };
+
+static inline void swap(int *a, int *b)
+{
+   int tmp = *a;
+   *a = *b;
+   *b = tmp;
+}
+
+/// Transform `order` into its next lexicographically larger permutation.
+///
+/// return true if on success
+/// return false if parameter is already the largest possible permutation
+static bool next_permutation(int order[NUM_HOUSES], int by_value[NUM_HOUSES])
+{
+   const size_t len = NUM_HOUSES;
+
+   // find the rightmost element that is smaller than its right neighbor
+   size_t idx1 = len - 2;
+   while (idx1 < len && order[idx1] >= order[idx1 + 1])
+      --idx1;
+
+   // if no such element has been found we've reached the final permutation
+   if (idx1 >= len)
+      return false;
+
+   // find the rightmost element that is larger than order[idx1]
+   size_t idx2 = len - 1;
+   while (order[idx1] >= order[idx2])
+      --idx2;
+
+   // permute the elements
+   swap(order + idx1, order + idx2);
+   for (size_t a = idx1 + 1, b = len - 1; a < b; ++a, --b)
+      swap(order + a, order + b);
+
+   // update the affected elements of by_value
+   for (size_t i = idx1; i < NUM_HOUSES; ++i)
+      by_value[order[i]] = i;
+   return true;
+}
+
+enum nationality { ENGLISH, JAPANESE, NORWEGIAN, SPANISH, UKRAINIAN };
+enum color { BLUE, GREEN, IVORY, RED, YELLOW };
+enum animal { DOG, FOX, HORSE, SNAILS, ZEBRA };
+enum drink { COFFEE, MILK, ORANGE_JUICE, TEA, WATER };
+enum smoke { CHESTERFIELD, KOOL, LUCKY_STRIKE, OLD_GOLD, PARLIAMENT };
+
+static void solve(const char **out_drinks_water, const char **out_owns_zebra)
+{
+   int num_solutions = 0;
+   int drinks_water = -1;
+   int owns_zebra = -1;
+
+   int colors[] = { BLUE, GREEN, IVORY, RED, YELLOW };
+   int house_by_color[] = { 0, 1, 2, 3, 4 };
+   do {
+      // 6. The green house is immediately to the right of the ivory house.
+      if (house_by_color[GREEN] - 1 != house_by_color[IVORY])
+         continue;
+
+      int nationalities[] = { ENGLISH, JAPANESE, NORWEGIAN, SPANISH,
+                              UKRAINIAN };
+      int house_by_nationality[] = { 0, 1, 2, 3, 4 };
+      do {
+         // 2. The Englishman lives in the red house.
+         if (house_by_nationality[ENGLISH] != house_by_color[RED])
+            continue;
+
+         // 10. The Norwegian lives in the first house.
+         if (house_by_nationality[NORWEGIAN] != 0)
+            continue;
+
+         // 15. The Norwegian lives next to the blue house.
+         if (abs(house_by_nationality[NORWEGIAN] - house_by_color[BLUE]) != 1)
+            continue;
+
+         int pets[] = { DOG, FOX, HORSE, SNAILS, ZEBRA };
+         int house_by_pet[] = { 0, 1, 2, 3, 4 };
+         do {
+            // 3. The Spaniard owns the dog.
+            if (house_by_nationality[SPANISH] != house_by_pet[DOG])
+               continue;
+
+            int beverages[] = { COFFEE, MILK, ORANGE_JUICE, TEA, WATER };
+            int house_by_beverage[] = { 0, 1, 2, 3, 4 };
+            do {
+               // 4. Coffee is drunk in the green house.
+               if (house_by_beverage[COFFEE] != house_by_color[GREEN])
+                  continue;
+
+               // 5. The Ukrainian drinks tea.
+               if (house_by_nationality[UKRAINIAN] != house_by_beverage[TEA])
+                  continue;
+
+               // 9. Milk is drunk in the middle house.
+               if (house_by_beverage[MILK] != NUM_HOUSES / 2)
+                  continue;
+
+               int brands[] = { CHESTERFIELD, KOOL, LUCKY_STRIKE, OLD_GOLD,
+                                PARLIAMENT };
+               int house_by_brand[] = { 0, 1, 2, 3, 4 };
+               do {
+                  // 7. The Old Gold smoker owns snails.
+                  if (house_by_brand[OLD_GOLD] != house_by_pet[SNAILS])
+                     continue;
+
+                  // 8. Kools are smoked in the yellow house.
+                  if (house_by_brand[KOOL] != house_by_color[YELLOW])
+                     continue;
+
+                  // 11. The man who smokes Chesterfields lives in the
+                  //     house next to the man with the fox.
+                  if (abs(house_by_brand[CHESTERFIELD] - house_by_pet[FOX]) !=
+                      1)
+                     continue;
+
+                  // 12. Kools are smoked in the house next to the house
+                  //     where the horse is kept.
+                  if (abs(house_by_brand[KOOL] - house_by_pet[HORSE]) != 1)
+                     continue;
+
+                  // 13. The Lucky Strike smoker drinks orange juice.
+                  if (house_by_brand[LUCKY_STRIKE] !=
+                      house_by_beverage[ORANGE_JUICE])
+                     continue;
+
+                  // 14. The Japanese smokes Parliaments.
+                  if (house_by_nationality[JAPANESE] !=
+                      house_by_brand[PARLIAMENT])
+                     continue;
+
+                  assert(num_solutions == 0);
+                  ++num_solutions;
+                  drinks_water = nationalities[house_by_beverage[WATER]];
+                  owns_zebra = nationalities[house_by_pet[ZEBRA]];
+
+               } while (next_permutation(brands, house_by_brand));
+            } while (next_permutation(beverages, house_by_beverage));
+         } while (next_permutation(pets, house_by_pet));
+      } while (next_permutation(nationalities, house_by_nationality));
+   } while (next_permutation(colors, house_by_color));
+
+   assert(num_solutions == 1);
+   switch (drinks_water) {
+      case ENGLISH:
+         *out_drinks_water = "English";
+         break;
+      case JAPANESE:
+         *out_drinks_water = "Japanese";
+         break;
+      case NORWEGIAN:
+         *out_drinks_water = "Norwegian";
+         break;
+      case SPANISH:
+         *out_drinks_water = "Spanish";
+         break;
+      case UKRAINIAN:
+         *out_drinks_water = "Ukrainian";
+         break;
+      default:
+         assert(false);
+   }
+   switch (owns_zebra) {
+      case ENGLISH:
+         *out_owns_zebra = "English";
+         break;
+      case JAPANESE:
+         *out_owns_zebra = "Japanese";
+         break;
+      case NORWEGIAN:
+         *out_owns_zebra = "Norwegian";
+         break;
+      case SPANISH:
+         *out_owns_zebra = "Spanish";
+         break;
+      case UKRAINIAN:
+         *out_owns_zebra = "Ukrainian";
+         break;
+      default:
+         assert(false);
+   }
+}
+
+const char *drinks_water(void)
+{
+   const char *result, *dummy;
+   solve(&result, &dummy);
+   return result;
+}
+
+const char *owns_zebra(void)
+{
+   const char *result, *dummy;
+   solve(&dummy, &result);
+   return result;
+}

exercises/practice/zebra-puzzle/.meta/example.h

@@ -0,0 +1,10 @@
+#ifndef ZEBRA_PUZZLE_H
+#define ZEBRA_PUZZLE_H
+
+/// Determine the nationality of the resident who drinks water.
+const char *drinks_water(void);
+
+/// Determine the nationality of the resident who owns the zebra.
+const char *owns_zebra(void);
+
+#endif

exercises/practice/zebra-puzzle/.meta/tests.toml

@@ -0,0 +1,16 @@
+# 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.
+
+[16efb4e4-8ad7-4d5e-ba96-e5537b66fd42]
+description = "resident who drinks water"
+
+[084d5b8b-24e2-40e6-b008-c800da8cd257]
+description = "resident who owns zebra"

exercises/practice/zebra-puzzle/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)