2024 day6 solve2

1 files changed, 78 insertions, 0 deletions

diff --git a/2024/day6/solve2.py b/2024/day6/solve2.py
new file mode 100644
index 0000000..faaf88a
--- /dev/null
+++ b/2024/day6/solve2.py
@@ -0,0 +1,78 @@
+import sys
+
+def traverse(room: list[list[str]], guard_current_row: int, guard_current_col: int, direct: tuple[int, int], check_for_loop: bool) -> bool:
+    row_count = len(room)
+    col_count = len(room[0])
+    previous_directions: list[list[list[tuple[int, int]]]] = []
+    for _ in range(row_count):
+        previous_directions.append([])
+        for _ in range(col_count):
+            previous_directions[-1].append([])
+
+    while True:
+        if not check_for_loop:
+            room[guard_current_row][guard_current_col] = "X"
+        else:
+            if direct in previous_directions[guard_current_row][guard_current_col]:
+                return True
+
+            previous_directions[guard_current_row][guard_current_col].append(direct)
+
+        new_row_idx = guard_current_row + direct[0]
+        new_col_idx = guard_current_col + direct[1]
+
+        if new_row_idx < 0 or new_row_idx >= row_count or new_col_idx < 0 or new_col_idx >= col_count:
+            break
+
+        if room[new_row_idx][new_col_idx] == "#":
+            dir_idx = directions.index(direct)
+            if dir_idx == len(directions) - 1:
+                dir_idx = 0
+            else:
+                dir_idx += 1
+            direct = directions[dir_idx]
+        else:
+            guard_current_row = new_row_idx
+            guard_current_col = new_col_idx
+
+    return False
+
+lines = []
+with open("input") as f:
+    for line in f.readlines():
+        lines.append(list(line.strip()))
+
+found_guard = False
+guard_row_idx = None
+guard_col_idx = None
+direction = None
+
+directions = [(-1, 0), (0, 1), (1, 0), (0, -1)]
+
+for line_idx, line in enumerate(lines):
+    for icon_idx, guard_icon in enumerate(("^", ">", "v", "<")):
+        if guard_icon in line:
+            guard_row_idx = line_idx
+            guard_col_idx = line.index(guard_icon)
+            direction = directions[icon_idx]
+            found_guard = True
+            break
+
+    if found_guard:
+        break
+
+if not found_guard:
+    sys.exit("Could not found guard.")
+
+traverse(lines, guard_row_idx, guard_col_idx, direction, False)
+
+count = 0
+for row_idx, line in enumerate(lines):
+    for col_idx, char in enumerate(line):
+        if char == "X":
+            lines[row_idx][col_idx] = "#"
+            if traverse(lines, guard_row_idx, guard_col_idx, direction, True):
+                count += 1
+            lines[row_idx][col_idx] = "X"
+
+print(count)