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-rw-r--r--09/part2.c354
1 files changed, 354 insertions, 0 deletions
diff --git a/09/part2.c b/09/part2.c
new file mode 100644
index 0000000..129a671
--- /dev/null
+++ b/09/part2.c
@@ -0,0 +1,354 @@
+#include <algds/sort.h>
+#include <errno.h>
+#include <ctype.h>
+
+#include <algds/vec.h>
+#include <algds/str.h>
+#include <algds/basic_traits.h>
+#include <algds/tree_map.h>
+#include <stdio.h>
+
+typedef struct {
+ int x;
+ int y;
+} Vec2;
+
+long rec_area(Vec2 a, Vec2 b) {
+ long dx = a.x - b.x;
+ long dy = a.y - b.y;
+ if (dx < 0) dx = -dx;
+ if (dy < 0) dy = -dy;
+ return (dx + 1) * (dy + 1);
+}
+
+#define PANIC do { \
+ fprintf(stderr, "panic at %s:%d\n", __FILE__, __LINE__); \
+ abort(); \
+} while (0)
+
+void expect_char(char e) {
+ int c = fpeek(stdin);
+ if (c != e) {
+ PANIC;
+ }
+ fgetc(stdin);
+}
+
+bool string2long(const char *s, long *num) {
+ char *end;
+ errno = 0;
+ *num = strtol(s, &end, 10);
+ if (end == s) {
+ return false;
+ }
+ if (errno != 0) {
+ return false;
+ }
+ return true;
+}
+
+int64_t parse_integer() {
+ long ret;
+ StrBuilder sb;
+ StrBuilder_init(&sb);
+ while (1) {
+ int c = fpeek(stdin);
+ if (isdigit(c)) {
+ fgetc(stdin);
+ StrBuilder_append_char(&sb, c);
+ } else {
+ break;
+ }
+ }
+ if (strlen(sb.buf) == 0) {
+ PANIC;
+ }
+ StrBuilder_append_char(&sb, '\0');
+ if (!string2long(sb.buf, &ret)) {
+ PANIC;
+ }
+ free(sb.buf);
+ return ret;
+}
+
+Vec2 parse_vec2() {
+ int x = parse_integer();
+ expect_char(',');
+ int y = parse_integer();
+ return (Vec2){.x = x, .y = y};
+}
+
+void Vec2_show(Vec2 self, FILE *fp) {
+ fprintf(fp, "(%d,%d)", self.x, self.y);
+}
+
+VECTOR_DEF(Vec2)
+VECTOR_IMPL(Vec2)
+
+typedef struct {
+ int64_t start;
+ int64_t end;
+} Range;
+
+void Range_show(Range self, FILE *fp) {
+ fprintf(fp, "%ld-%ld", self.start, self.end);
+}
+
+VECTOR_DEF(Range)
+VECTOR_IMPL(Range)
+
+int Range_cmp(Range a, Range b) {
+ if (a.start < b.start) {
+ return -1;
+ } else if (a.start == b.start) {
+ return 0;
+ } else {
+ return 1;
+ }
+}
+
+QSORT_DEF(Range)
+QSORT_IMPL(Range)
+
+void merge_ranges(RangeVector *ranges) {
+ Range_qsort(ranges->buffer, RangeVector_len(ranges));
+ if (RangeVector_len(ranges) < 1) {
+ return;
+ }
+ RangeVector merged;
+ RangeVector_init(&merged);
+ Range current = ranges->buffer[0];
+ for (int i = 1; i < RangeVector_len(ranges); i++) {
+ if (ranges->buffer[i].start > current.end) {
+ RangeVector_push_back(&merged, current);
+ current = ranges->buffer[i];
+ continue;
+ } else if (ranges->buffer[i].end > current.end) {
+ current.end = ranges->buffer[i].end;
+ }
+ }
+ RangeVector_push_back(&merged, current);
+ RangeVector_free(ranges);
+ *ranges = merged;
+}
+
+TREE_MAP_DEF(Int, RangeVector)
+TREE_MAP_IMPL(Int, RangeVector)
+
+Int2RangeVectorTreeMap hlines;
+Int2RangeVectorTreeMap vlines;
+
+void init_lines() __attribute__((constructor));
+void init_lines() {
+ Int2RangeVectorTreeMap_init(&hlines);
+ Int2RangeVectorTreeMap_init(&vlines);
+}
+
+VECTOR_DEF(RangeVector)
+VECTOR_IMPL(RangeVector)
+
+RangeVectorVector vsegs;
+RangeVectorVector hsegs;
+
+void init_segs() __attribute__((constructor));
+void init_segs() {
+ RangeVectorVector_init(&vsegs);
+ RangeVectorVector_init(&hsegs);
+}
+
+int height = -1;
+int width = -1;
+
+void add_line(Vec2 a, Vec2 b) {
+ int start, end;
+ if (a.x == b.x) {
+ if (a.y < b.y) {
+ start = a.y;
+ end = b.y;
+ } else {
+ start = b.y;
+ end = a.y;
+ }
+ Int2RangeVectorTreeMapIter it = Int2RangeVectorTreeMap_find(&vlines, a.x);
+ if (it == NULL) {
+ RangeVector rs;
+ RangeVector_init(&rs);
+ Int2RangeVectorTreeMap_insert(&vlines, a.x, rs);
+ it = Int2RangeVectorTreeMap_find(&vlines, a.x);
+ }
+ RangeVector_push_back(&it->value, (Range){ .start = start, .end = end });
+ } else if (a.y == b.y) {
+ if (a.x < b.x) {
+ start = a.x;
+ end = b.x;
+ } else {
+ start = b.x;
+ end = a.x;
+ }
+ Int2RangeVectorTreeMapIter it = Int2RangeVectorTreeMap_find(&hlines, a.y);
+ if (it == NULL) {
+ RangeVector rs;
+ RangeVector_init(&rs);
+ Int2RangeVectorTreeMap_insert(&hlines, a.y, rs);
+ it = Int2RangeVectorTreeMap_find(&hlines, a.y);
+ }
+ RangeVector_push_back(&it->value, (Range){ .start = start, .end = end });
+ } else {
+ PANIC;
+ }
+}
+
+bool is_sub_range(Range r, RangeVector *ranges) {
+ for (int i = 0; i < ranges->size; i++) {
+ Range target = ranges->buffer[i];
+ if (target.end >= r.end && target.start <= r.start) {
+ return true;
+ }
+ }
+ return false;
+}
+
+bool in_open_ranges(int x, RangeVector *ranges) {
+ for (int i = 0; i < ranges->size; i++) {
+ Range r = ranges->buffer[i];
+ if (x < r.end && x >= r.start) {
+ return true;
+ }
+ }
+ return false;
+}
+
+void scan_lines() {
+ // hsegs
+ for (int i = 0; i < height; i++) {
+ Int2RangeVectorTreeMapIter it = Int2RangeVectorTreeMap_find(&hlines, i);
+ if (it != NULL) {
+ for (int j = 0; j < it->value.size; j++) {
+ RangeVector_push_back(&hsegs.buffer[i], it->value.buffer[j]);
+ }
+ }
+ int cross_cnt = 0;
+ int enter_pos;
+ it = Int2RangeVectorTreeMap_min(&vlines);
+ for (; it != NULL; it = Int2RangeVectorTreeMap_next(&vlines, it)) {
+ if (in_open_ranges(i, &it->value)) {
+ if (cross_cnt % 2 == 0) {
+ enter_pos = it->key;
+ }
+ cross_cnt++;
+ if (cross_cnt % 2 == 0) {
+ RangeVector_push_back(&hsegs.buffer[i], (Range){.start = enter_pos, .end = it->key});
+ }
+ }
+ }
+ merge_ranges(&hsegs.buffer[i]);
+ }
+ // vsegs
+ for (int i = 0; i < width; i++) {
+ Int2RangeVectorTreeMapIter it = Int2RangeVectorTreeMap_find(&vlines, i);
+ if (it != NULL) {
+ for (int j = 0; j < it->value.size; j++) {
+ RangeVector_push_back(&vsegs.buffer[i], it->value.buffer[j]);
+ }
+ }
+ int cross_cnt = 0;
+ int enter_pos;
+ it = Int2RangeVectorTreeMap_min(&hlines);
+ for (; it != NULL; it = Int2RangeVectorTreeMap_next(&hlines, it)) {
+ if (in_open_ranges(i, &it->value)) {
+ if (cross_cnt % 2 == 0) {
+ enter_pos = it->key;
+ }
+ cross_cnt++;
+ if (cross_cnt % 2 == 0) {
+ RangeVector_push_back(&vsegs.buffer[i], (Range){.start = enter_pos, .end = it->key});
+ }
+ }
+ }
+ merge_ranges(&vsegs.buffer[i]);
+ }
+}
+
+bool is_valid_rec(Vec2 a, Vec2 b) {
+ int x1, x2, y1, y2, t;
+ x1 = a.x;
+ x2 = b.x;
+ y1 = a.y;
+ y2 = b.y;
+ if (x1 > x2) {
+ t = x2;
+ x2 = x1;
+ x1 = t;
+ }
+ if (y1 > y2) {
+ t = y2;
+ y2 = y1;
+ y1 = t;
+ }
+ if (!is_sub_range((Range){.start = x1, .end = x2}, &hsegs.buffer[y1])) {
+ return false;
+ }
+ if (!is_sub_range((Range){.start = x1, .end = x2}, &hsegs.buffer[y2])) {
+ return false;
+ }
+ if (!is_sub_range((Range){.start = y1, .end = y2}, &vsegs.buffer[x1])) {
+ return false;
+ }
+ if (!is_sub_range((Range){.start = y1, .end = y2}, &vsegs.buffer[x2])) {
+ return false;
+ }
+ return true;
+}
+
+int main() {
+ Vec2Vector tiles;
+ Vec2Vector_init(&tiles);
+ while (1) {
+ int c = fpeek(stdin);
+ if (!isdigit(c)) {
+ break;
+ }
+ Vec2 v = parse_vec2();
+ c = fpeek(stdin);
+ if (c == '\n') {
+ fgetc(stdin);
+ }
+ Vec2Vector_push_back(&tiles, v);
+ }
+
+ for (int i = 0; i < tiles.size; i++) {
+ if (tiles.buffer[i].x > width) {
+ width = tiles.buffer[i].x;
+ }
+ if (tiles.buffer[i].y > height) {
+ height = tiles.buffer[i].y;
+ }
+ }
+ width++; height++;
+ for (int i = 0; i < width; i++) {
+ RangeVector segs;
+ RangeVector_init(&segs);
+ RangeVectorVector_push_back(&vsegs, segs);
+ }
+ for (int i = 0; i < height; i++) {
+ RangeVector segs;
+ RangeVector_init(&segs);
+ RangeVectorVector_push_back(&hsegs, segs);
+ }
+ for (int i = 0; i < tiles.size - 1; i++) {
+ add_line(tiles.buffer[i], tiles.buffer[i+1]);
+ }
+ add_line(tiles.buffer[0], tiles.buffer[tiles.size - 1]);
+ scan_lines();
+ long max_area = 0;
+ for (int i = 0; i < tiles.size; i++) {
+ for (int j = i + 1; j < tiles.size; j++) {
+ long area = rec_area(tiles.buffer[i], tiles.buffer[j]);
+ if (area > max_area && is_valid_rec(tiles.buffer[i], tiles.buffer[j])) {
+ max_area = area;
+ }
+ }
+ }
+ printf("%ld\n", max_area);
+ return 0;
+} \ No newline at end of file
generated by cgit v1.0 at 2025-12-29 17:22:01 +0000