[Sync Iteration] c/zebra-puzzle/1

solutions/c/zebra-puzzle/1/zebra_puzzle.c

@@ -0,0 +1,113 @@
+#include "zebra_puzzle.h"
+#include <stdbool.h>
+
+// typedef struct {
+//    const char *drinks_water;
+//    const char *owns_zebra;
+// } solution_t;
+
+typedef enum { COLORS, NATIONS, DRINKS, HOBBIES, PETS, DONE } level_t;
+
+enum { RED, GREEN, IVORY, YELLOW, BLUE };
+enum { DOG, SNAIL, FOX, HORSE, ZEBRA };
+enum { COFFEE, TEA, MILK, ORANGE_JUICE, WATER };
+enum { ENGLISH, SPANIARD, UKRAINIAN, NORWEGIAN, JAPANESE };
+enum { DANCING, PAINTING, READING, FOOTBALL, CHESS };
+
+int state[5][5];
+
+static inline bool next_to(int a, int b) {
+    return (a - b == 1) || (b - a == 1);
+}
+
+static inline void swap(int *n1, int *n2) {
+    int temp = *n1;
+    *n1 = *n2;
+    *n2 = temp;
+}
+
+// There are five houses.
+// The Englishman lives in the red house.
+// The Spaniard owns the dog.
+// The person in the green house drinks coffee.
+// The Ukrainian drinks tea.
+// The green house is immediately to the right of the ivory house.
+// The snail owner likes to go dancing.
+// The person in the yellow house is a painter.
+// The person in the middle house drinks milk.
+// The Norwegian lives in the first house.
+// The person who enjoys reading lives in the house next to the person with the fox.
+// The painter's house is next to the house with the horse.
+// The person who plays football drinks orange juice.
+// The Japanese person plays chess.
+// The Norwegian lives next to the blue house.
+
+static inline bool is_valid(level_t level) {
+    if (level >= COLORS) {
+        if (state[COLORS][GREEN] != state[COLORS][IVORY] + 1) return false;
+    }
+    if (level >= NATIONS) {
+        if (state[NATIONS][NORWEGIAN] != 0) return false;
+        if (state[NATIONS][ENGLISH] != state[COLORS][RED]) return false;
+        if (!next_to(state[NATIONS][NORWEGIAN], state[COLORS][BLUE])) return false;
+    }
+    if (level >= DRINKS) {
+        if (state[DRINKS][MILK] != 2) return false;
+        if (state[DRINKS][COFFEE] != state[COLORS][GREEN]) return false;
+        if (state[NATIONS][UKRAINIAN] != state[DRINKS][TEA]) return false;
+    }
+    if (level >= HOBBIES) {
+        if (state[COLORS][YELLOW] != state[HOBBIES][PAINTING]) return false;
+        if (state[HOBBIES][FOOTBALL] != state[DRINKS][ORANGE_JUICE]) return false;
+        if (state[NATIONS][JAPANESE] != state[HOBBIES][CHESS]) return false;
+    }
+    if (level >= PETS) {
+        if (state[NATIONS][SPANIARD] != state[PETS][DOG]) return false;
+        if (state[PETS][SNAIL] != state[HOBBIES][DANCING]) return false;
+        if (!next_to(state[HOBBIES][READING], state[PETS][FOX])) return false;
+        if (!next_to(state[HOBBIES][PAINTING], state[PETS][HORSE])) return false;
+    }
+    return true;
+}
+
+static bool backtrack(level_t level, int* current_perm, int start) {
+    if (level == DONE) return true;
+
+    if (start == 5) {
+        if (is_valid(level)) {
+            int next_p[5] = {0, 1, 2, 3, 4};
+            return backtrack(level + 1, next_p, 0);
+        }
+        return false;
+    }
+
+    for (int i = start; i < 5; i++) {
+        swap(&current_perm[start], &current_perm[i]);
+
+        state[level][start] = current_perm[start];
+
+        if (backtrack(level, current_perm, start + 1)) return true;
+
+        swap(&current_perm[start], &current_perm[i]);
+    }
+    return false;
+}
+
+solution_t solve_puzzle(void){
+
+    int first_perm[5] = {0, 1, 2, 3, 4};
+    backtrack(COLORS, first_perm, 0);
+
+    solution_t sol;
+//  enum { ENGLISH, SPANIARD, UKRAINIAN, NORWEGIAN, JAPANESE };
+    const char* nations[] = {"Englishman", "Spaniard", "Ukrainian", "Norwegian", "Japanese"};
+
+    for(int i=0; i<5; i++) {
+        if (state[NATIONS][i] == state[DRINKS][WATER]) sol.drinks_water = nations[i];
+        if (state[NATIONS][i] == state[PETS][ZEBRA]) sol.owns_zebra = nations[i];
+    }
+
+    return sol;
+
+}
+

solutions/c/zebra-puzzle/1/zebra_puzzle.h

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+#ifndef ZEBRA_PUZZLE_H
+#define ZEBRA_PUZZLE_H
+
+typedef struct {
+   const char *drinks_water;
+   const char *owns_zebra;
+} solution_t;
+
+solution_t solve_puzzle(void);
+
+#endif