From cf52f4996e2e9506848939ef9242da6e6af2b42a Mon Sep 17 00:00:00 2001
From: Andrew Lalis <andrewlalisofficial@gmail.com>
Date: Mon, 6 Dec 2021 10:26:03 +0100
Subject: [PATCH] Added day 6.

---
 source/app.d               |  4 ++--
 source/day6/input.txt      |  1 +
 source/day6/part1.d        | 28 ++++++++++++++++++++++++++++
 source/day6/test_input.txt |  1 +
 4 files changed, 32 insertions(+), 2 deletions(-)
 create mode 100644 source/day6/input.txt
 create mode 100644 source/day6/part1.d
 create mode 100644 source/day6/test_input.txt

diff --git a/source/app.d b/source/app.d
index 9d7dd67..ccb63b7 100644
--- a/source/app.d
+++ b/source/app.d
@@ -1,7 +1,7 @@
 import std.stdio;
 
-import day5.part1;
+import day6.part1;
 
 void main() {
-	hydrothermalVents();
+	lanternFish();
 }
diff --git a/source/day6/input.txt b/source/day6/input.txt
new file mode 100644
index 0000000..229caa9
--- /dev/null
+++ b/source/day6/input.txt
@@ -0,0 +1 @@
+1,2,1,1,1,1,1,1,2,1,3,1,1,1,1,3,1,1,1,5,1,1,1,4,5,1,1,1,3,4,1,1,1,1,1,1,1,5,1,4,1,1,1,1,1,1,1,5,1,3,1,3,1,1,1,5,1,1,1,1,1,5,4,1,2,4,4,1,1,1,1,1,5,1,1,1,1,1,5,4,3,1,1,1,1,1,1,1,5,1,3,1,4,1,1,3,1,1,1,1,1,1,2,1,4,1,3,1,1,1,1,1,5,1,1,1,2,1,1,1,1,2,1,1,1,1,4,1,3,1,1,1,1,1,1,1,1,5,1,1,4,1,1,1,1,1,3,1,3,3,1,1,1,2,1,1,1,1,1,1,1,1,1,5,1,1,1,1,5,1,1,1,1,2,1,1,1,4,1,1,1,2,3,1,1,1,1,1,1,1,1,2,1,1,1,2,3,1,2,1,1,5,4,1,1,2,1,1,1,3,1,4,1,1,1,1,3,1,2,5,1,1,1,5,1,1,1,1,1,4,1,1,4,1,1,1,2,2,2,2,4,3,1,1,3,1,1,1,1,1,1,2,2,1,1,4,2,1,4,1,1,1,1,1,5,1,1,4,2,1,1,2,5,4,2,1,1,1,1,4,2,3,5,2,1,5,1,3,1,1,5,1,1,4,5,1,1,1,1,4
diff --git a/source/day6/part1.d b/source/day6/part1.d
new file mode 100644
index 0000000..309e209
--- /dev/null
+++ b/source/day6/part1.d
@@ -0,0 +1,28 @@
+module day6.part1;
+
+import std.file;
+import std.stdio;
+import std.math;
+import std.string;
+import std.algorithm;
+import std.conv;
+import std.array;
+import std.parallelism;
+
+ulong computeGrowth(ulong initial, ulong t) {
+    return (t <= initial) ? 1 : computeGrowth(6, t - initial - 1) + computeGrowth(8, t - initial - 1);
+}
+
+void lanternFish() {
+    auto f = File("source/day6/input.txt", "r");
+    ulong t = 256;
+    ulong[] fish = f.readln().strip().split(",").map!(s => s.to!ulong).array;
+    ulong total = 0;
+    // WARNING!!! Only use this on a PC with >= 24 threads.
+    writefln("Using %d threads.", taskPool.size());
+    foreach (idx, i; taskPool.parallel(fish, 1)) {
+        total += computeGrowth(i, t);
+        writefln("Computed growth for fish %d", idx);
+    }
+    writefln("%d", total);
+}
\ No newline at end of file
diff --git a/source/day6/test_input.txt b/source/day6/test_input.txt
new file mode 100644
index 0000000..55129f1
--- /dev/null
+++ b/source/day6/test_input.txt
@@ -0,0 +1 @@
+3,4,3,1,2