1 files changed, 112 insertions, 0 deletions
diff --git a/09/part1.c b/09/part1.c
new file mode 100644
index 0000000..039d1b0
--- /dev/null
+++ b/09/part1.c
@@ -0,0 +1,112 @@
+#include <algds/sort.h>
+#include <errno.h>
+#include <ctype.h>
+
+#include <algds/vec.h>
+#include <algds/str.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)
+
+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);
+    }
+    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) {
+                max_area = area;
+            }
+        }
+    }
+    printf("%ld\n", max_area);
+    return 0;
+}
+\ No newline at end of file