Puzzle 22: Change coordinate system so that 'y' goes up

Having 'y' go down was easier with navigating through the memory buffer
we were using to store the map, but some of the work we'll have to do
with the cube net is easier for me to get my head around with a more
traditional coordinate system.

1 files changed, 6 insertions, 6 deletions

diff --git a/22.c b/22.c
index a021510..df55cdb 100644
--- a/22.c
+++ b/22.c
@@ -114,7 +114,7 @@ map_elem(struct map const * map, int x, int y)
 			|| y < 0 || y >= map->rows)
 		return ' ';
 
-	return map->_buf[x + y * map->cols];
+	return map->_buf[x + (map->rows - 1 - y) * map->cols];
 }
 
 
@@ -170,8 +170,8 @@ elf_move(struct elf * elf, struct map const * map, int distance)
 		struct elf newelf;
 
 		switch (elf->dir) {
-		case D_NORTH: dy = -1; break;
-		case D_SOUTH: dy = +1; break;
+		case D_NORTH: dy = +1; break;
+		case D_SOUTH: dy = -1; break;
 		case D_EAST: dx = +1; break;
 		case D_WEST: dx = -1; break;
 		default:
@@ -304,7 +304,7 @@ main(int argc, char ** argv)
 
 	// Set initial position
 	elf.x = 0;
-	elf.y = 0;
+	elf.y = map.rows - 1;
 	elf.dir = D_EAST;
 	while (elf.x < map.cols && map_elem(&map, elf.x, elf.y) != '.')
 		++elf.x;
@@ -344,8 +344,8 @@ main(int argc, char ** argv)
 
 	// Done.
 	printf("Password is %d (%d,%d,%d)\n",
-			1000 * (1 + elf.y) + 4 * (1 + elf.x) + elf.dir,
-			1 + elf.x, 1 + elf.y, elf.dir);
+			1000 * (map.rows - elf.y) + 4 * (1 + elf.x) + elf.dir,
+			1 + elf.x, map.rows - elf.y, elf.dir);
 
 	// Tidy and exit.
 	map_tidy(&map);