1 files changed, 49 insertions, 0 deletions
diff --git a/2022/day09/main.c b/2022/day09/main.c
new file mode 100644
index 0000000..7f19df5
--- /dev/null
+++ b/2022/day09/main.c
@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct Cord_ Cord;
+
+typedef struct Cord_ {
+    int x,y;
+    Cord *next, *prev;
+} Cord;
+
+Cord* updateTail(Cord *head, Cord *tail)
+{
+    int dy, dx, d;
+    dx = head->x - tail->x;
+    dy = head->y - tail->y;
+    d = dx * dx + dy * dy;
+    // distance <= 1
+    if ( d <= 2) return tail;
+    tail->x += (dx + dx/abs(dx))/2;
+    tail->y += (dy + dy/abs(dy))/2;
+
+    return tail;
+}
+
+int main()
+{
+    char c;
+    int d;
+    Cord *h, *t;
+    t = &(Cord){0};
+    h = &(Cord){0};
+    while (scanf("%c %d\n", &c, &d) != EOF)
+    {
+        printf("%c %d\n", c, d);
+        for (int i = 0; i < d; i++)
+        {
+            h->x += (c == 'R') - (c == 'L');
+            h->y += (c == 'U') - (c == 'D');
+            printf("H %d %d \n", h->x, h->y);
+            t = updateTail(h, t);
+            printf("T %d %d \n", t->x, t->y);
+        }
+    }
+
+}
+
+// ./main < input2.txt | grep T | sort | uniq | wc -l
+
+