Added day 6

source/app.d

@@ -12,6 +12,7 @@ import day2;
 import day3;
 import day4;
 import day5;
+import day6;
 import dayutil;
 
 immutable string progName = "aoc-2020";
@@ -22,6 +23,7 @@ Variant function(int, File, string[])[] programs = [
 	&day3.run,
 	&day4.run,
 	&day5.run,
+	&day6.run,
 ];
 
 void printUsage(string name) {
@@ -51,7 +53,7 @@ void main(string[] args) {
 	}
 
 	if (day <= 0 || day > programs.length) {
-		printUsage(args[0], "[day] must be between 1 and %d".format(programs.length - 1));
+		printUsage(args[0], "[day] must be between 1 and %d".format(programs.length));
 	}
 
 	int part;

source/day6.d

@@ -0,0 +1,73 @@
+import std.algorithm;
+import std.array;
+import std.range;
+import std.string;
+import std.stdio;
+import std.traits;
+import std.variant;
+
+import dayutil;
+
+Variant run(int part, File file, string[] args) {
+	auto lines = file.byLineCopy.array;
+	Variant result = parts!size_t(part,
+			() => part1(lines),
+			() => part2(lines));
+	return result;
+}
+
+size_t part1(Range)(Range range) if (isInputRange!Range){
+	return range.splitter!(x => x.length == 0)
+		.map!(x => x.joiner.array.sort.uniq.count).sum;
+}
+
+unittest {
+	string input = q"EOS
+abc
+
+a
+b
+c
+
+ab
+ac
+
+a
+a
+a
+a
+
+b
+EOS";
+	assert(input.lineSplitter.part1() == 11);
+}
+
+size_t part2(Range)(Range range) if (isInputRange!Range){
+	return range.splitter!(x => x.length == 0)
+		.map!((x) {
+			size_t people = x.length;
+
+			return x.joiner.array.sort.group.filter!(x => x[1] == people).count;
+		}).sum;
+}
+
+unittest {
+	string input = q"EOS
+abc
+
+a
+b
+c
+
+ab
+ac
+
+a
+a
+a
+a
+
+b
+EOS";
+	assert(input.lineSplitter.part2() == 6);
+}