import 2021

2021/day5/day5.py

@@ -0,0 +1,41 @@
+from collections import defaultdict
+
+def main(infile):
+    points = defaultdict(int)
+    with open(infile) as f:
+        for line in f:
+            start, end = line.split(" -> ")
+            start_x, start_y = [int(x) for x in start.split(",")]
+            end_x, end_y = [int(x) for x in end.split(",")]
+
+            # column |
+            if start_x == end_x:
+                step = 1 if start_y < end_y else -1
+                for y in range(start_y, end_y + step, step):
+                    points[(start_x, y)] = points[(start_x, y)] + 1
+            # line -
+            elif start_y == end_y:
+                step = 1 if start_x < end_x else -1
+                for x in range(start_x, end_x + step, step):
+                    points[(x, start_y)] = points[(x, start_y)] + 1
+            # diagonal \
+            elif ((start_x < end_x and start_y > end_y) 
+                    or (start_x > end_x and start_y < end_y)):
+                step = 1 if start_y > end_y else -1
+                for dx in range(0, end_x - start_x + step, step):
+                    points[(start_x + dx, start_y - dx)] = points[(start_x + dx, start_y + dx)] + 1
+            # diagonal /
+            elif ((start_x < end_x and start_y < end_y)
+                    or (start_x > end_x and start_y > end_y)):
+                step = 1 if start_y < end_y else -1
+                for dx in range(0, end_x - start_x + step, step):
+                    points[(start_x + dx, start_y + dx)] = points[(start_x + dx, start_y + dx)] + 1
+                    
+    res = len([x for x in points.values() if x >= 2])
+    print(res)
+
+
+
+
+if __name__ == "__main__":
+    main("input.txt")