day 5, parts 1 & 2 (C)

2021/day05/README.txt

@@ -41,4 +41,34 @@ To avoid the most dangerous areas, you need to determine the number of points wh
 
 Consider only horizontal and vertical lines. At how many points do at least two lines overlap?
 
-To begin, get your puzzle input.
+Your puzzle answer was 4655.
+
+--- Part Two ---
+
+Unfortunately, considering only horizontal and vertical lines doesn't give you the full picture; you need to also consider diagonal lines.
+
+Because of the limits of the hydrothermal vent mapping system, the lines in your list will only ever be horizontal, vertical, or a diagonal line at exactly 45 degrees. In other words:
+
+    An entry like 1,1 -> 3,3 covers points 1,1, 2,2, and 3,3.
+    An entry like 9,7 -> 7,9 covers points 9,7, 8,8, and 7,9.
+
+Considering all lines from the above example would now produce the following diagram:
+
+1.1....11.
+.111...2..
+..2.1.111.
+...1.2.2..
+.112313211
+...1.2....
+..1...1...
+.1.....1..
+1.......1.
+222111....
+
+You still need to determine the number of points where at least two lines overlap. In the above example, this is still anywhere in the diagram with a 2 or larger - now a total of 12 points.
+
+Consider all of the lines. At how many points do at least two lines overlap?
+
+Your puzzle answer was 20500.
+
+Both parts of this puzzle are complete! They provide two gold stars: **