Day 2, puzzle 1

source/app.d

@@ -6,12 +6,14 @@ import std.stdio;
 import std.getopt;
 
 import day1;
+import day2;
 import dayutil;
 
 immutable string progName = "aoc-2020";
 
 void function(string[])[] programs = [
-	&day1.run
+	&day1.run,
+	&day2.run
 ];
 
 void printUsage(string name) {

source/day1.d

@@ -15,7 +15,7 @@ void run(string[] args) {
 
 	/* For each line on stdin, copy it, map it to an integer and sort it.
 	   Sorting a range makes it a SortedRange and functions like contains(range, elem)
-       will make use of optimised implementations, in the case of contains(range, elem)
+	   will make use of optimised implementations, in the case of contains(range, elem)
 	   it will use a binary search instead of a linear search */
 	auto numbers = stdin.byLineCopy.map!(a => to!int(a)).array.sort;
 

source/day2.d

@@ -0,0 +1,27 @@
+import std.algorithm;
+import std.format;
+import std.stdio;
+
+
+import dayutil;
+
+bool isPasswordValid(T)(T line) {
+	int min, max;
+	char c;
+	string password;
+	line.formattedRead("%d-%d %c: %s", min, max, c, password);
+	ulong charCount = password.count(c);
+	return min <= charCount && charCount <= max;
+}
+
+void run(string[] args) {
+	ulong count = stdin.byLine
+		.count!(l => isPasswordValid(l));
+	writeln(count);
+}
+
+unittest {
+	assert(isPasswordValid("1-3 a: abcde") == true);
+	assert(isPasswordValid("1-3 b: cdefg") == false);
+	assert(isPasswordValid("2-9 c: ccccccccc") == true);
+}