From 612f25b5cae8ad7fe0e0ab0394b79c908a314a06 Mon Sep 17 00:00:00 2001
From: ilikecats <ilikecats@mx.sdf.org>
Date: Sun, 7 Jul 2024 17:39:59 -0700
Subject: [PATCH] Initial commit

---
 .gitignore |  5 +++++
 Makefile   |  2 ++
 README.md  | 13 +++++++++++++
 main.cpp   | 24 ++++++++++++++++++++++++
 4 files changed, 44 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 README.md
 create mode 100644 main.cpp

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..9e2643b
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+# Ignore emacs backups
+*~
+
+# Ignore build
+collatz*
\ No newline at end of file
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..0828869
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,2 @@
+default:
+	g++ main.cpp -o collatz
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..3aecfef
--- /dev/null
+++ b/README.md
@@ -0,0 +1,13 @@
+# Collatz conjecture solver
+### (x%2==0) ? x/=2 : x=x*3+1;
+
+Program to solver the (Collatz conjecture)[https://en.wikipedia.org/wiki/Collatz_conjecture].
+
+Algorithm:
+- Start with number.
+- If number is even, divide by two.
+- If number is odd, multiply by three and add one.
+- Repeat.
+
+To figure out if it will repeat, save all the previous numbers, and check if the current number is one of those.
+If it is, that means it will repeat, and you have disproved the Collatz conjecture. So far, though, nobody has disproven it up to 2^68.
diff --git a/main.cpp b/main.cpp
new file mode 100644
index 0000000..47b404f
--- /dev/null
+++ b/main.cpp
@@ -0,0 +1,24 @@
+#include <iostream>
+#include <string>
+
+// TODO:
+//  Use GMP for numbers (to allow for really big numbers)
+//  Make disproving mode
+//  Make no print mode (for speed, implement after disproving mode)
+
+int main(int argc, char* argv[]) {
+  // If number not provided
+  if (argc < 2) {
+    std::cout << "Usage: " << argv[0] << " <number>\n";
+    exit(1);
+  }
+  long long x { std::stoll(argv[1]) };
+  std::cout << x << '\n';
+  while (x != 1) {
+    if (x % 2 == 0)
+      x /= 2;
+    else if (x % 2)
+      x = x*3+1;
+    std::cout << x << '\n';
+  }
+}