add aoc 2022

1 files changed, 106 insertions, 0 deletions

diff --git a/advent-of-code/2022/09/2.c b/advent-of-code/2022/09/2.c
new file mode 100644
index 0000000..7659e9b
--- /dev/null
+++ b/advent-of-code/2022/09/2.c
@@ -0,0 +1,106 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <htable.h>
+#include <crc32.h>
+
+typedef struct {
+    int x;
+    int y;
+} Point;
+
+uint32_t point_hash(void *point) {
+    return crc32(0, point, sizeof(Point));
+}
+
+bool point_eq(void *x, void *y) {
+    Point *a = x, *b = y;
+    return (a->x == b->x) && (a->y == b->y);
+}
+
+typedef struct {
+    Point knots[10];
+} State;
+
+bool is_adjacent(Point p1, Point p2) {
+    if (abs(p1.x - p2.x) <= 1 && abs(p2.y - p1.y) <= 1) {
+        return true;
+    }
+    return false;
+}
+
+Point catchup(Point prev, Point new) {
+    int dx = new.x - prev.x;
+    int dy = new.y - prev.y;
+    int cx = 0, cy = 0;
+    if (dx > 0) cx = 1;
+    if (dx < 0) cx = -1;
+    if (dy > 0) cy = 1;
+    if (dy < 0) cy = -1;
+    return (Point){prev.x + cx, prev.y + cy};
+}
+
+void run_impl(State *s, HTable *record, int dx, int dy) {
+    s->knots[0].x += dx;
+    s->knots[0].y += dy;
+    for (int i = 1; i < 10; i++) {
+        if (is_adjacent(s->knots[i], s->knots[i-1])) {
+            continue;
+        }
+        s->knots[i] = catchup(s->knots[i], s->knots[i-1]);
+        if (i == 9) {
+            htable_insert(record , &(s->knots[i]));
+        }
+    }
+}
+
+void run(State *s, HTable *record, char direction, int step) {
+    int dx, dy;
+    switch (direction) {
+        case 'U':
+            dx = 0; dy = 1;
+            break;
+        case 'D':
+            dx = 0; dy = -1;
+            break;
+        case 'L':
+            dx = -1; dy = 0;
+            break;
+        case 'R':
+            dx = 1; dy = 0;
+            break;
+        default:
+            return;
+    }
+    for (int i = 0; i < step; i++) {
+        run_impl(s, record, dx, dy);
+    }
+}
+
+int count_htable(HTable *ht) {
+    int count = 0;
+    for (void *iter = htable_begin(ht);
+            iter != NULL;
+            iter = htable_next(ht, iter)) {
+        Point *p = iter;
+        count++;
+    }
+    return count;
+}
+
+int main() {
+    FILE *fp = fopen("input", "r");
+    State state = {0};
+    char direction;
+    int step;
+    HTable record;
+    htable_init(&record, sizeof(Point), -1, point_hash, point_eq);
+    htable_insert(&record, &state.knots[9]);
+    while (fscanf(fp, "%c %d", &direction, &step) != EOF) {
+        run(&state, &record, direction, step);
+    }
+    int count = count_htable(&record);
+    printf("%d\n", count);
+    return 0;
+}
+