2022/04 comments

encse · encse · commit 672d35cb0474 · 2022-12-31T21:11:21.000+01:00
diff --git a/2022/Day04/Solution.cs b/2022/Day04/Solution.cs
@@ -5,26 +5,30 @@ namespace AdventOfCode.Y2022.Day04;
 
 [ProblemName("Camp Cleanup")]
 class Solution : Solver {
+    
+    // Each line of the input represents two ranges - job done by two elves.
+    // We need to find those lines where the elves did some work twice.
+    // Part 1 and 2 differs in how we define 'duplicated work'.
+    record struct Range(int from, int to);
+
     public object PartOne(string input) => DuplicatedWorkCount(input, Contains);
     public object PartTwo(string input) => DuplicatedWorkCount(input, Overlaps);
 
-    record struct Range(int from, int to);
-
     // True if r1 contains r2 [ { } ] 
     bool Contains(Range r1, Range r2) => r1.from <= r2.from && r2.to <= r1.to; 
     
     // True if r1 overlaps r2 { [ } ], the other direction is not checked.
     bool Overlaps(Range r1, Range r2) => r1.to >= r2.from && r1.from <= r2.to; 
 
-    // DuplicatedWorkCount goes over the lines in the input, converts them to 
-    // ranges A and B, and counts how many times rangeCheck(A,B) or 
-    // rangeCheck(B, A) is true. The check is applied in both ways so that the 
-    // Contains and Overlaps functions don't have to check each directions.
+    // DuplicatedWorkCount parses each input line into ranges and applies 
+    // rangeCheck on them to find duplicated work. RangeCheck doesnt have to be 
+    // symmetrical in its arguments, but DuplicatedWorkCount makes it so calling
+    // it twice with the arguments swapped.
     private int DuplicatedWorkCount(
         string input, 
         Func<Range, Range, bool> rangeCheck
     ) {
-        // '36-41,35-40' becomes [Range(36, 41), Range(35, 40)]
+        // E.g. '36-41,35-40' becomes [Range(36, 41), Range(35, 40)]
         var parseRanges = (string line) => 
             from range in line.Split(',') 
             let fromTo = range.Split('-').Select(int.Parse)
