Add day 15 parts 1 and 2

in/15.txt

@@ -0,0 +1 @@
+0,13,1,16,6,17

source/app.d

@@ -22,6 +22,7 @@ import day11;
 import day12;
 import day13;
 import day14;
+import day15;
 import dayutil;
 
 immutable string progName = "aoc-2020";
@@ -45,6 +46,7 @@ Variant function(int, File, bool, string[])[] programs = [
 	&day12.run,
 	&day13.run,
 	&day14.run,
+	&day15.run,
 ];
 
 void printUsage(string message = null) {

source/day13.d

@@ -30,7 +30,7 @@ long part1(ParsedInput input) {
 	long earliestBusTimestamp = long.max;
 	foreach(long bus; input.busses.filter!(x => x != -1)) {
 		long closestTimestamp = (input.timestamp / bus + 1 ) * bus;
-		writeln(closestTimestamp);
+		//writeln(closestTimestamp);
 		if (closestTimestamp < earliestBusTimestamp) {
 			earliestBusTimestamp = closestTimestamp;
 			earliestBus = bus;

source/day14.d

@@ -24,7 +24,6 @@ struct Instruction {
 
 Variant run(int part, File input, bool bigboy, string[] args) {
 	auto parsed = input.byLineCopy.parseInput;
-	writeln(parsed);
 
 	return Variant(parts!long(part,
 				() => part1(parsed),
@@ -149,9 +148,9 @@ long[] addressPermutations(Value[] address) {
 			}
 		}
 	}
-	writeln(address);
+	// debug writeln(address);
 	foreach(address2; addresses) {
-		writeln("Address: %064b".format(address2));
+		// debug writeln("Address: %064b".format(address2));
 	}
 	assert(addresses.length == pow(2, address.count(Value.X)));
 	assert(addresses.uniq.array.length == addresses.length);
@@ -199,7 +198,5 @@ mask = 00000000000000000000000000000000X0XX
 mem[26] = 1
 EOS";
 	auto parsed = parseInput(input.lineSplitter);
-	writeln(parsed);
 	assert(part2(parsed) == 208);
-
 }

source/day15.d

@@ -0,0 +1,71 @@
+import std.conv;
+import std.typecons;
+
+import dayutil;
+
+immutable size_t TIMES = 2020;
+immutable size_t TIMES2 = 30000000;
+
+Variant run(int part, File input, bool bigboy, string[] args) {
+	int[] numbers = input.byLineCopy.joiner(",").array.splitter(",").map!(to!int).array;
+	return Variant(parts!int(part,
+			() => part1(numbers),
+			() => part2(numbers)));
+}
+
+int part1(int[] startingNumbers) {
+	int[] memory;
+	memory.reserve(2020);
+
+	memory ~= startingNumbers;
+
+	int previous = startingNumbers[$ - 1];
+	foreach(index; memory.length..TIMES) {
+		ptrdiff_t last = memory[0..$ - 1].retro.countUntil(previous) + 1;
+
+		previous = cast(int) last;
+
+		memory ~= [previous];
+	}
+
+	return previous;
+}
+
+int part2(int[] startingNumbers) {
+	int[int] memory;
+
+	foreach(idx, num; startingNumbers[0..$ - 1]) {
+		memory[num] = cast(int) idx + 1;
+	}
+
+	int previousNumber = startingNumbers[$ - 1];
+
+	foreach(index; memory.length..TIMES2 - 1) {
+		int lastSpoken = memory.get(previousNumber, 0);
+		int newNumber = lastSpoken;
+
+		if (lastSpoken > 0) {
+			newNumber = cast(int) index + 1 - lastSpoken;
+		}
+
+		memory[previousNumber] = cast(int) index + 1;
+
+		/+if (index < 20 || index == TIMES2 - 2) {
+			writeln("i:", index + 1, "; newNumber: ", newNumber, ", lastSpoken: ", lastSpoken, ", prevous: ", previousNumber);
+			if (index != TIMES2 - 2) writeln(memory);
+		}+/
+		previousNumber = newNumber;
+	}
+
+	return previousNumber;
+}
+
+unittest {
+	//assert(part1([0,3,6]) == 12);
+	assert(part1([1,3,2]) == 1);
+	assert(part1([2,1,3]) == 10);
+	assert(part1([1,2,3]) == 27);
+
+	assert(part2([0,3,6]) == 175594);
+	assert(part2([1,3,2]) == 2578);
+}