Puzzle 22: Store proposed next position as an elf

That way we will keep a proposed orientation change alongside the
position change.

1 files changed, 10 insertions, 8 deletions

diff --git a/22.c b/22.c
index cd4a15d..83da420 100644
--- a/22.c
+++ b/22.c
@@ -86,7 +86,8 @@ int
 elf_move(struct elf * elf, char const * map, int cols, int rows, enum map_type mtype, int distance)
 {
 	while (distance > 0) {
-		int skip, wrap, base, newpos;
+		int skip, wrap, base;
+		struct elf newelf;
 
 		switch (elf->dir) {
 		case D_NORTH:
@@ -116,14 +117,15 @@ elf_move(struct elf * elf, char const * map, int cols, int rows, enum map_type m
 
 		base = (elf->pos / wrap) * wrap;
 
-		newpos = base + modulo(elf->pos + skip, wrap);
+		newelf.pos = base + modulo(elf->pos + skip, wrap);
+		newelf.dir = elf->dir;
 
-		if (map[newpos] == ' ' || map[newpos] == '\n') {
+		if (map[newelf.pos] == ' ' || map[newelf.pos] == '\n') {
 			switch (mtype) {
 			case M_FLAT:
 				// Just keep going until we wrap around to a non-blank position
-				while (map[newpos] == ' ' || map[newpos] == '\n')
-					newpos = base + modulo(newpos + skip, wrap);
+				while (map[newelf.pos] == ' ' || map[newelf.pos] == '\n')
+					newelf.pos = base + modulo(newelf.pos + skip, wrap);
 				break;
 
 			case M_NET:
@@ -136,9 +138,9 @@ elf_move(struct elf * elf, char const * map, int cols, int rows, enum map_type m
 			}
 		}
 
-		switch (map[newpos]) {
+		switch (map[newelf.pos]) {
 		case '.':
-			elf->pos = newpos;
+			*elf = newelf;
 			--distance;
 			break;
 
@@ -147,7 +149,7 @@ elf_move(struct elf * elf, char const * map, int cols, int rows, enum map_type m
 			break;
 
 		default:
-			fprintf(stderr, "Unexpected map character %c\n", map[newpos]);
+			fprintf(stderr, "Unexpected map character %c\n", map[newelf.pos]);
 			return -1;
 		}
 	}