day 19: constraints

src/day19/solve.c

@@ -111,28 +111,54 @@ static inline void interval_negate_rule(interval_t *interval, rule_t *rule) {
     }
 }
 
-static inline constraint_t constraint_apply_rule(constraint_t constraint, rule_t *r) {
+static inline constraint_t constraint_apply_rule(constraint_t constraint, rule_t *rule) {
     constraint_t result = constraint;
-    switch (r->variable) {
-    case 'x': interval_apply_rule(&result.x, r); break;
-    case 'm': interval_apply_rule(&result.m, r); break;
-    case 'a': interval_apply_rule(&result.a, r); break;
-    case 's': interval_apply_rule(&result.s, r); break;
+    switch (rule->variable) {
+    case 'x': interval_apply_rule(&result.x, rule); break;
+    case 'm': interval_apply_rule(&result.m, rule); break;
+    case 'a': interval_apply_rule(&result.a, rule); break;
+    case 's': interval_apply_rule(&result.s, rule); break;
     }
     return result;
 }
 
-static inline constraint_t constraint_negate_rule(constraint_t constraint, rule_t *r) {
+static inline constraint_t constraint_negate_rule(constraint_t constraint, rule_t *rule) {
     constraint_t result = constraint;
-    switch (r->variable) {
-    case 'x': interval_negate_rule(&result.x, r); break;
-    case 'm': interval_negate_rule(&result.m, r); break;
-    case 'a': interval_negate_rule(&result.a, r); break;
-    case 's': interval_negate_rule(&result.s, r); break;
+    switch (rule->variable) {
+    case 'x': interval_negate_rule(&result.x, rule); break;
+    case 'm': interval_negate_rule(&result.m, rule); break;
+    case 'a': interval_negate_rule(&result.a, rule); break;
+    case 's': interval_negate_rule(&result.s, rule); break;
     }
     return result;
 }
 
+static inline void process_path(int path[], int path_idx, ust_workflow_t *workflows, CharSlice99 *id_to_name,
+                                constraint_t c) {
+    log_debug(">> found new path to destination:");
+    CharSlice99 from = id_to_name[path[0]];
+    for (int i = 1; i < path_idx; i++) {
+        log_debug("constraints: %d <= x <= %d, %d <= m <= %d, %d <= a <= %d, %d <= s <= %d", c.x.lower, c.x.upper,
+                  c.m.lower, c.m.upper, c.a.lower, c.a.upper, c.s.lower, c.s.upper);
+        CharSlice99 to = id_to_name[path[i]];
+        log_debug("%.*s -> %.*s", from.len, from.ptr, to.len, to.ptr);
+        workflow_t *wf = &ust_workflow_t_find(workflows, (workflow_t){.name = to})->key;
+        for (int i = 0; i < wf->rule_count; i++) {
+            rule_t *rule = &wf->rule[i];
+            if (CharSlice99_primitive_eq(rule->destination, from)) {
+                c = constraint_apply_rule(c, rule);
+                // TODO: there might also be some other rule which matches
+                break;
+            } else {
+                c = constraint_negate_rule(c, rule);
+            }
+        }
+        from = to;
+    }
+    log_debug("constraints: %d <= x <= %d, %d <= m <= %d, %d <= a <= %d, %d <= s <= %d", c.x.lower, c.x.upper,
+              c.m.lower, c.m.upper, c.a.lower, c.a.upper, c.s.lower, c.s.upper);
+}
+
 static void find_all_paths(graph_t *graph, int current, int destination, bool visited[], int path[], int *path_idx,
                            ust_workflow_t *workflows, CharSlice99 *id_to_name) {
     // mark the current node and store it in path[]
@@ -141,12 +167,9 @@ static void find_all_paths(graph_t *graph, int current, int destination, bool vi
     *path_idx = *path_idx + 1;
 
     if (current == destination) {
-        log_debug(">> found new path to destination:");
-        for (int i = 0; i < *path_idx; i++) {
-            int id = path[i];
-            CharSlice99 name = id_to_name[id];
-            log_debug("%.*s", name.len, name.ptr);
-        }
+        interval_t initial = {.lower = 0, .upper = 4000};
+        constraint_t constraint = {.x = initial, .m = initial, .a = initial, .s = initial};
+        process_path(path, *path_idx, workflows, id_to_name, constraint);
     } else {
         adj_list_t *lst = &graph->adj[current];
         for (int i = 0; i < lst->neighbor_count; i++) {