Solve puzzle 9 part 1

I wasn't creating a new tail element after inserting the first tail, so
when we revisited the origin the second time it didn't spot it as a
dupe, giving an off-by-one error

(The test input didn't have the tail pass the origin twice, so this
wasn't an issue there)

1 files changed, 1 insertions, 0 deletions

diff --git a/9.c b/9.c
index d0c6a9f..bd19cae 100644
--- a/9.c
+++ b/9.c
@@ -50,6 +50,7 @@ main()
 	int ntails = 0;
 
 	tsearch(tail, &tails, point_tcmp);
+	tail = point_copy(tail);
 	++ntails;
 	fprintf(stderr, "Tail visiting %d,%d\n", tail->x, tail->y);