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day 19: constraints
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@michaeladler
michaeladler committed Dec 27, 2023
1 parent 301ea6b commit 7adb2ad
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Showing 2 changed files with 121 additions and 37 deletions.
154 changes: 119 additions & 35 deletions src/day19/solve.c
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Original file line number Diff line number Diff line change
Expand Up @@ -59,8 +59,8 @@ typedef struct {
} graph_t;

typedef struct {
int lower; // inclusive
int upper; // inclusive
int a; // inclusive
int b; // inclusive
} interval_t;

typedef struct {
Expand Down Expand Up @@ -97,62 +97,148 @@ static inline CharSlice99 *workflow_next(workflow_t *wf, data_t data) {

static inline void interval_apply_rule(interval_t *interval, rule_t *rule) {
if (rule->kind == LT) {
interval->upper = MIN(rule->value - 1, interval->upper); // interval.upper < rule->value
interval->b = rule->value - 1; // interval.upper < rule->value
} else if (rule->kind == GT) {
interval->lower = MAX(rule->value + 1, interval->lower); // interval.lower > rule->value
interval->a = rule->value + 1; // interval.lower > rule->value
}
}

static inline void interval_negate_rule(interval_t *interval, rule_t *rule) {
if (rule->kind == LT) {
interval->upper = MAX(rule->value, interval->upper); // interval.upper >= rule->value
interval->a = rule->value; // interval.lower >= rule->value
} else if (rule->kind == GT) {
interval->lower = MIN(rule->value, interval->lower); // interval.lower <= rule->value
interval->b = rule->value; // interval.upper <= rule->value
}
}

static inline constraint_t constraint_apply_rule(constraint_t constraint, rule_t *r) {
static inline char kind_to_char(rule_kind_e kind) {
switch (kind) {
case LT: return '<';
case GT: return '>';
case JUMP: return 'J';
}
}

static inline i64 interval_cardinality(interval_t interval) {
if (interval.b < interval.a) return 0;
return interval.b - interval.a + 1;
}

static inline i64 constraint_cardinality(constraint_t c) {
return interval_cardinality(c.x) * interval_cardinality(c.m) * interval_cardinality(c.a) *
interval_cardinality(c.s);
}

static inline bool constraint_is_valid(constraint_t c) {
if (c.x.b < c.x.a) return false;
if (c.m.b < c.m.a) return false;
if (c.a.b < c.a.a) return false;
if (c.s.b < c.s.a) return false;
return true;
}

static inline constraint_t constraint_apply_rule(constraint_t constraint, rule_t *rule) {
if (rule->kind != JUMP) {
log_debug("applying rule: %c %c %d to jump to %.*s", rule->variable, kind_to_char(rule->kind), rule->value,
rule->destination.len, rule->destination.ptr);
}
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;
}
log_debug("constraints: %d<=x<=%d, %d<=m<=%d, %d<=a<=%d, %d<=s<=%d", result.x.a, result.x.b, result.m.a, result.m.b,
result.a.a, result.a.b, result.s.a, result.s.b);
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) {
if (rule->kind != JUMP) {
log_debug("negating rule: %c %c %d to jump to %.*s", rule->variable, kind_to_char(rule->kind), rule->value,
rule->destination.len, rule->destination.ptr);
}
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;
}
log_debug("constraints: %d <= x <= %d, %d <= m <= %d, %d <= a <= %d, %d <= s <= %d", result.x.a, result.x.b,
result.m.a, result.m.b, result.a.a, result.a.b, result.s.a, result.s.b);
return result;
}

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) {
static inline i64 process_path(int path[], int path_len, ust_workflow_t *workflows, CharSlice99 *id_to_name,
constraint_t initial) {
log_debug(">> found new path to destination:");
CharSlice99 from = id_to_name[path[0]];
constraint_t constraints[128];
constraints[0] = initial;
int constraints_count = 1;
for (int i = 1; i < path_len; i++) {
workflow_t *wf = &ust_workflow_t_find(workflows, (workflow_t){.name = from})->key;
CharSlice99 to = id_to_name[path[i]];
log_debug("looking for rules %.*s -> %.*s", from.len, from.ptr, to.len, to.ptr);
int old_count = constraints_count;
for (int j = 0; j < old_count; j++) {
constraint_t c = constraints[j];
bool is_first_match = true;
for (int k = 0; k < wf->rule_count; k++) {
rule_t *rule = &wf->rule[k];
if (CharSlice99_primitive_eq(rule->destination, to)) {
constraint_t new_c = constraint_apply_rule(c, rule);
if (!constraint_is_valid(new_c)) continue;
if (is_first_match) {
constraints[j] = new_c;
is_first_match = false;
} else { // append
log_debug("constraints_count:%d", constraints_count);
constraints[constraints_count++] = new_c;
}
} else {
c = constraint_negate_rule(c, rule);
}
}
}
from = to;
}

i64 total = 0;
log_debug(">> final result:");
for (int i = 0; i < constraints_count; i++) {
constraint_t c = constraints[i];
total += constraint_cardinality(c);
log_debug("- %d <= x <= %d, %d <= m <= %d, %d <= a <= %d, %d <= s <= %d", c.x.a, c.x.b, c.m.a, c.m.b, c.a.a,
c.a.b, c.s.a, c.s.b);
}
log_debug(">> total: %ld", total);
return total;
}

static i64 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) {

i64 total = 0;

// mark the current node and store it in path[]
visited[current] = true;
path[*path_idx] = current;
*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 = {.a = 1, .b = 4000};
constraint_t constraint = {.x = initial, .m = initial, .a = initial, .s = initial};
total += 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++) {
int neighbor_id = lst->neighbor[i];
if (!visited[neighbor_id]) {
find_all_paths(graph, neighbor_id, destination, visited, path, path_idx, workflows, id_to_name);
total +=
find_all_paths(graph, neighbor_id, destination, visited, path, path_idx, workflows, id_to_name);
}
}
}
Expand All @@ -161,10 +247,12 @@ static void find_all_paths(graph_t *graph, int current, int destination, bool vi
// unvisited
*path_idx = *path_idx - 1;
visited[current] = false;

return total;
}

void solve(char *buf, size_t buf_size, Solution *result) {
int part1 = 0, part2 = 0;
int part1 = 0;
size_t pos = 0;

_cleanup_(ust_workflow_t_free) ust_workflow_t workflows = ust_workflow_t_init(workflow_t_hash, workflow_t_equal);
Expand All @@ -183,7 +271,6 @@ void solve(char *buf, size_t buf_size, Solution *result) {
wf.name = CharSlice99_new(&buf[start], pos - start);

ust_name_id_t_insert(&name_to_id, (name_id_t){.id = id_count, .name = wf.name});
log_debug("id_count: %d", id_count);
id_to_name[id_count++] = wf.name;

pos++;
Expand Down Expand Up @@ -248,12 +335,9 @@ void solve(char *buf, size_t buf_size, Solution *result) {
if (buf[pos] == '}') break;
pos++;
}
log_debug(">> input: x=%d, m=%d, a=%d, s=%d", data.x, data.m, data.a, data.s);

workflow_t *current = &start_node->key;
while (1) {
CharSlice99 next = *workflow_next(current, data);
log_debug("%.*s -> %.*s", current->name.len, current->name.ptr, next.len, next.ptr);
if (CharSlice99_primitive_eq(next, accepted)) {
part1 += data.x + data.a + data.m + data.s;
break;
Expand Down Expand Up @@ -287,10 +371,10 @@ void solve(char *buf, size_t buf_size, Solution *result) {
bool visited[MAX_NODES];
for (size_t i = 0; i < sizeof(visited); i++) visited[i] = false;
int path[MAX_NODES], path_idx = 0;
find_all_paths(&graph, start_id, dest_id, visited, path, &path_idx, &workflows, id_to_name);
i64 part2 = find_all_paths(&graph, start_id, dest_id, visited, path, &path_idx, &workflows, id_to_name);

aoc_itoa(part1, result->part1, 10);
aoc_itoa(part2, result->part2, 10);
snprintf(result->part1, sizeof(result->part1), "%d", part1);
snprintf(result->part2, sizeof(result->part2), "%ld", part2);
}

int solve_input(const char *fname, Solution *result) {
Expand Down
4 changes: 2 additions & 2 deletions src/day19/solve_test.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -32,15 +32,15 @@ hdj{m>838:A,pv}\n\
Solution solution;
solve(buf, strlen(buf), &solution);
ASSERT_STR("19114", solution.part1);
ASSERT_STR("0", solution.part2);
ASSERT_STR("167409079868000", solution.part2);
}

#ifdef HAVE_INPUTS
CTEST(day19, real) {
Solution solution;
solve_input("input/" DAY ".txt", &solution);
ASSERT_STR("391132", solution.part1);
ASSERT_STR("0", solution.part2);
// ASSERT_STR("0", solution.part2);
}
#endif

Expand Down

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